probably for an obsolete tucho (for which the middle voice of another alternate teucho (to make ready or bring to pass) is used in certain tenses; akin to the base of tikto through the idea of effecting; properly, to affect; or (specially), to hit or light upon (as a mark to be reached), i.e. (transitively) to attain or secure an object or end, or (intransitively) to happen (as if meeting with); but in the latter application only impersonal (with ei), i.e. perchance; or (present participle) as adjective, usual (as if commonly met with, with ou, extraordinary), neuter (as adverb) perhaps; or (with another verb) as adverb, by accident (as it were)
be, chance, enjoy, little, obtain, X refresh...self, + special. Compare tupto.