tho

From Middle English tho, tha, from Old English þā (“the, those”, plural), from Proto-West Germanic *þai, from Proto-Germanic *þai (“those”), from Proto-Indo-European *to-, *só (“that”). Cognate with Saterland Frisian do (“the”, plural). Doublet of they.

Simplified reform spelling. Popular in American English in the earlier 20th century. Like thru, it failed to establish itself fully, but remains in informal contexts or where brevity is needed. Compare tho'.