Reconstruction:Proto-Japonic/-tay

Etymology
Regular continuative / adverbial / conjunctive conjugation of completion auxiliary -tu. Bjarke Frellesvig and Alexander Vovin both describe an ancient copular element, manifesting in this verb suffix, and in the Old Japanese genitive particle  and adverbial / quotative particle.

Suffix

 * 1)  (in verbs)
 * 1)  (in verbs)