late 13c., from Old English þanone, þanon "from that place" + adverbial genitive -es. Old English þanone/þanon is from Proto-Germanic *thanana (source also of Old Saxon thanana, Old Norse þana, Old Frisian thana, Old High German danana, German von dannen), related obscurely to the root of then, and ultimately from PIE demonstrative base *to- (see the). Written with -c- to indicate a voiceless "s" sound. Meaning "from that time" is from late 14c.; sense of "for that reason" is from 1650s. From thence is redundant.
