late 13c., from Old English þanone, þanon "from that place" + adverbial genitive -es. Old English þanone/þanon is from Proto-Germanic *thanana (cognates: 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.