Usage: 3 forms in 3 verses
Form Translated As     In Verse(s)
τρισσεύσω shall be three times LXX.1Sam.20.20
τρισσεύσεισ you shall do it three times LXX.1Sam.20.19
ετρίσσευσαν they did it a third time LXX.1Kgs.18.34

Liddell-Scott-Jones

τρισσεύω (trisseuō) to do three times G:V

τρισσεύω-εύω,

do a thing thrice or for the third time, [LXX]; compare τρισσεύωόω.

LSJ Scripture Refs: LXX.1Kgs.20.19*