Why is the ninth month called September?
Old English twegen (masc.) "two" (masc. nominative and accusative), from Proto-Germanic *twa- (see two). The word outlasted the breakdown of gender in Middle English and survived as a secondary form of two, especially in cases where the numeral follows a noun. Its continuation into modern times was aided by its use in KJV and the Marriage Service, in poetry (where it is a useful rhyme word), and in oral use where it is necessary to be clear that two and not to or too is meant.