Why is the ninth month called September?
Old English bringan "to bring, bring forth, produce, present, offer" (past tense brohte, past participle broht), from Proto-Germanic *brenganan (cf. Old Frisian brenga, Middle Dutch brenghen, Old High German bringan, Gothic briggan); no exact cognates outside Germanic, but it appears to be from PIE root *bhrengk-, compound based on root *bher- (1) "to carry" (cf. Latin ferre; see infer).
The tendency to conjugate this as a strong verb on the model of sing, drink, etc., is ancient: Old English also had a rare strong past participle form, brungen, corresponding to modern colloquial brung. To bring down the house figuratively (1754) is to elicit applause so thunderous it collapses the roof.