If that is a script on the stocking -- it looks hebrew or arabic (or pseudo-arabic)
(As mentioned earlier, Piero at least did have Mamluk arabic script surrounding his emblems on the oculus, so possible)
I'm assuming you are referring to this article (and I was entertaining the same thoughts, so may as well post some of that here): Bradley J. Cavallo, "Of Medici and Mamluk Power: Islamic Forms in a Renaissance Florentine Stained-Glass Window." (Viator, Jan 2014: 311-330). https://www.academia.edu/6733333/_Of_Me ... ss_Window_
By the very early 1460s, Piero had turned from the patronage of the Chapel-Shrine of the Annunciation to patronage of a more personal nature with the construction for himself of an oratory immediately adjoining the Chapel-Shrine of the Annunciation....One of the most obvious features of this was a large Votives Cabinet (no
longer extant) that contained the most precious and expensive votive offerings that had been left for the image of the Annunciation. Piero controlled not just the Votives Cabinet itself but also the mechanism that opened or closed it to reveal or conceal the accumulated ex-votives.17 In this way, Piero’s ‘stewardship’ of this structure within his oratory added to the attraction of seeing his space and led people to inspect the sumptuously-decorated interior as best they could from beyond a tall, bronze and marble balustrade surrounding the chapel-shrine.18 Nonetheless, Piero’s patronage created an unambiguous visual and physical association between the Medici and the miraculous image of the Annunciation through the strategic deployment of his coats-of-arms. [314-15]
The fleur-de-lis given to Piero by King Louis XI in early 1465 is missing from the impresa
installed which helps secure the dating, but then there is the surrounding script which concerns us:
...the border of the design deviates significantly because it consists of a series of small glass panels in which appear a repeating series of epithets in a style of Arabic calligraphy that resembles both naskḫī and thuluth.27 In the translation of the Arabic calligraphy Casalini and Bernardini have rather significantly disagreed. Casalini has argued that the translation he offered fit the context of a religious space dedicated to Mary because he believed that part of it read, “… who fills the universe (the wise), the born of Mary … and: all of the cosmos exalts in the glory [of] Mary…”28 Contrary to this, Bernardini has asserted that the Arabic calligraphy contains neither any reference to Mary nor communicates even a discernible message, per se; that, in fact, the Arabic calligraphy actually consists of a series of repeating honorific titles including “… the royal … the lord … the industrious … his Excellency … [and] …the wise …”29 Baldovinetti transcribed the calligraphy accurately and with a minimal degree of cultural “pollution” to the original form of the letters, meaning that they were legible even from a distance as Arabic. What’s more, it does not appear on another represented object, such as a carpet, silk hanging, or garment. This is to say that Baldovinetti simultaneously “freed” the identifiably-Arabic calligraphy from reference to the Islamic-made artworks but maintained the calligraphy’s association with Islamic aesthetics.30 Baldovinetti’s appropriation of Arabic calligraphy for inclusion in Piero’s coats-of-arms thus disrupted the conventional process of signification so that instead of linking to the traditional signified “Islamic art,” the signifier “Arabic calligraphy” linked Piero de’Medici to Islamic power. [316-17]
All a bit dense to digest (especially if your Near-Eastern language skills are nil) and the gloss of the symbolism at the end does not really clarify; nevertheless the Florentine art comparables with ps-Arabic below are more helpful, particularly the hem-line on Verrocchio's bronze which is also on the CVI Love dancers pointed out by Huck:
....some of the most easily-accessible examples are Gentile da Fabriano’s addition of pseudo-Arabic on a groom’s sash in the Strozzi Altarpiece (1423), Filarete’s incorporation of pseudo-script (pseudo-Persian) onto carpets/tapestries hanging behind the middle-register, low-relief figures of St. Paul and St. Peter in the monumental bronze doors of the central portal of the Basilica of St. Peter’s in the Vatican (1433–1445), and Andrea del Verrocchio’s inclusion of pseudo-Arabic into the hem-lines of the garments and boots worn by the bronze statue of David (before 1476). 
What did it all signify?
Words like “Saracen” or “Ottoman” could simultaneously signify heretic, corsair, sacker of Constantinople, or alternatively, a source of Aristotelian knowledge, spices, and the finest of textiles and other luxury goods. It had
been merchants hailing from many central- or northern-Italian cities like Pisa, Florence, and Venice who irrevocably stimulated the senses of their compatriots with novel commodities like pepper, cloves, nutmeg, and silk that had been directly imported from Islamic lands.43 Demand by Italian customers created a lively market not only for raw materials but also for far more refined and exotic Mediterranean products 
This shot-gun approach at meaning seems ill-suited to Piero's intent, at least; but Cavallo eventually comes around to just that:
First and foremost, the impetus for the composition of Baldovinetti’s design arguably derived from Piero’s possession of many “… things from Damascus …”52 This generic classification applied to artisanal objects made in either of the Mamluk controlled cities of Damascus or Cairo, two of the largest and most important centers
of economic and artistic exchange between Egypt, Syria, and the rest of the Mediterranean as far back as the eleventh century.53 By the early-fourteenth century, it had become commonplace for metal- or glassware created in those cities to include inscriptions in stylized calligraphy the language of which consisted of lengthy, formulaic lauds of amirs or sultans drawing from an extensive list of honorific titles (Arabic laqab, لقب ). It is this language that most closely resembles the epithets appearing in the inscription of Piero de’Medici’s stained-glass oculus.
...ever since the normalization of trade relations between Florence and the Islamic state of Tunis and then the
Mamluk Sultanate beginning at least by 1421–1422.57 From that time onwards, Florence became an active member of a Mediterranean-wide trade network exchanging diplomatic correspondence and commercial treaties at relatively regular intervals with Muslim rulers.58 Latin or Italian translations accompanied the original, Arabic-language correspondences.59 Because of this, Florentine readers of these documents gained first-hand experience with how their Mamluk counterparts applied particular Arabic phrases and vocabulary, specifically the honorific titles used to address and/or describe sovereigns in a way that conveyed their exalted social positions and political power.60 
I find that conclusion to be a stretch, considering your hoi polloi
merchant could not even read Latin, hence the boom of translations into the vulgar from the 1430s on. And the relevant key issue of Arabic translated into Italian is buried in this footnote 59: "Although it is not possible at the present time to know the identities of all those who made Italian or Latin translations of originally Arabic-language texts, Amari noted the recorded employment of such individuals by the Pisans and Florentines during the 13th through early-15th century" [but no examples provided]
The conclusion is even weaker - based on a 1489 sultan letter calling Lorenzo ḥâkim
(governor), Cavallo retroactively waxes thusly:
Because the Mamluks could have perceived and treated Piero in this way (as they did Lorenzo) and because the regal language found in diplomatic correspondences could apply interchangeability across socio-linguistic demarcations (as it did for Lorenzo), Piero could have encouraged a perception of his authority as princely. The Arabic epithets Piero did have incorporated into the design of his oculus contribute the strongest evidence that this is exactly how he envisioned, or wished to promote, himself. Piero’s stained-glass window represents, avant la lettre, a visual analogue to the language of praise applied to Lorenzo before it became politically permissible and physically safe for an acknowledgement of Medici power within Florence. Contextually, the design and installation of the oculus occurred contemporaneously with Piero early- to mid-1460s acquisition of a modicum of dominance over the Florentine patrician oligarchs ....Despite the size of the Arabic calligraphy, because it was recognizable as Arabic, select members of this group could have understood the promoted ideology of Medici control of Florence. Thus, in a beautiful work of hubris, the oculus acted as one instrument of Piero’s attempt
to transform his tentative political power into a robust image of self-projected authority, absolute and equal to any “oriental” autocrat: Piero di Cosimo de’Medici as Florentine caliph, sultan, or amir.
This militates against how Cosimo raised Piero - to control things behind the scenes, not flaunt one's power. And I surmise the number of peers who could have read the Arabic (a few specialized notaries? who were not peers) and associated it with Piero as a 'sultan' to be slim to none.
What we are left with, in my opinion, is ps-Arabic script as a fashionable device connoting the wealth of the Biblical East, and let's admit the dancers that bear that on their hems on the CVI Love trump are not all Medici, even if Medici partisans (which they undoubtedly represent), and are not wearing Piero's livery. So if Piero did have ps-Arabic or even legible Arabic on his calze
(which were important as part of one's livery/imprese
), then it merely associated him with exotic goods his bank was associated with in procuring. Further speculation - until/if the letters can be transliterated from the Gozzoli painting or CVI - is that the Arabic merely transliterated one of Piero's mottos, most likely semper
, as that is
legible on the horse reins near his calze
. If, in turn, the script is pure gibberish, then it merely connects Piero to the fabled treasures of the Biblical East, from hence the Medici-appropriated gift-bearing Magi hailed from.
PS Lorenzo Magnifico looking on to the Pantheon of Dead Medici as Magi
in Botticelli's Adoration of the Magi
painting from 1475 (left to right: grandfather Cosimo reaching for infant Jesus's feet, father Piero, uncle Giovanni - all dead by 1475 - then Lorenzo [standing with head tilted down at his father Piero], and finally next in line, the bending forward brother Giulani, dead in 3 more years at the hands of the Pazzi):