"type of thin, transparent fabric," c. 1600; earlier a common name for the festival of the Epiphany (early 14c.; in Anglo-French from late 13c.), from Old French Tifinie, Tiphanie "Epiphany" (c. 1200), from Late Latin Theophania "Theophany," another name for the Epiphany, from Greek theophania "the manifestation of a god" (see theophany).
Also popular in Old French and Middle English as a name given to girls born on Epiphany Day. The fabric sense is found only in English and is of obscure origin and uncertain relation to the other meanings, unless "holiday silk" or as a fanciful or playful allusion to "manifestation:"
The invention of that fine silke, Tiffanie, Sarcenet, and Cypres, which instead of apparell to cover and hide, shew women naked through them. [Holland's "Pliny," 1601]
The fashionable N.Y. jewelry firm Tiffany & Co. (1895) is named for its founder, goldsmith Charles L. Tiffany (1812-1902) and his son, Louis C. Tiffany (1848-1933), who was the art nouveau decorator noted for his glassware. The surname is attested in English from 1206.