Why is the ninth month called September?
late 13c., from Old English þanone, þanon "from that place" + adverbial genitive -es. Old English þanone/þanon is from West Germanic *thanana (cf. 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. From thence is redundant.