Tau gallicum

The only known mention of the letter is found in Catalepton, a set of epigrams attributed to Virgil and collected after his death in Appendix Vergiliana.

[2] The second epigram contains the following text: Corinthiorum amator iste uerborum, iste iste rhetor, namque quatenus totus Thucydides, tyrannus Atticae febris: tau Gallicum, min et sphin ut male illisit, ita omnia ista uerba miscuit fratri.

[1] The letter can be found in the initial of the name of the Celtic goddess Sirona, whose name is written as: Sirona, Ꟈirona or Thirona, highlighting the difficulty of noting the initial sound in the Latin alphabet.

The letter is also present in the lead of Chamalières, a lead tablet discovered in 1971 in Chamalières and written in the Gallic language with Latin cursive letters: snIeꟈꟈdic, aꟈꟈedillI.

It is supposed that it denotes an alveolar affricate /t͡s/, in free variation with [st] in initial position.