IPA: /ˈhɪðərˌtuː/
KK: /ˈhɪðərˌtu/
Up to this point in time; until now.
The project had hitherto been successful, but now it faces challenges.
Hitherto is formed from "hither" (from Old English "hither", meaning to this place) and "to" (meaning until or up to). The word "hitherto" means up to this point in time or until now.
Think of 'hither' meaning 'to this place' and 'to' meaning 'up to' — together they help you remember that 'hitherto' refers to a point in time up to now.