Hence
Middle English hennes (in hence (sense 3)): from earlier henne (from Old English heonan, of Germanic origin, related to he) + -s3 (later respelled -ce to denote the unvoiced sound).
wiktionary
A later Middle English spelling, retaining the voiceless -s, of hennes ( henne + adverbial genitive ending -s), from Old English heonan(“away", "hence”), from a Proto-West Germanic *hin-, from Proto-Germanic *hiz.
Cognate with Old Saxon hinan, Old High German hinnan (German hinnen), Dutch heen, Swedish hän. Related to Old English her(“here”).
etymonline
hence (adv.)
"(away) from here," late 13c., hennes, with adverbial genitive -s + Old English heonan "away, hence," from West Germanic *hin- (source also of Old Saxon hinan, Old High German hinnan, German hinnen), from PIE *ki-, variant of root *ko- "this," the stem of the demonstrative pronoun (see here).
The modern spelling (mid-15c.) is phonetic, to retain the breathy -s- (compare twice, once, since). Original "away from this place;" of time, "from this moment onward," late 14c.; meaning "from this (fact or circumstance)" first recorded 1580s. Wyclif (1382) uses hennys & þennys for "from here and there, on both sides."
