Why is the ninth month called September?
1520s, origin obscure. OED suggests imitative; perhaps a mix of boggle and bumble, or more likely from a Scandinavian word akin to Swedish bangla "to work ineffectually," Old Swedish bunga "to strike" (cf. German Bengel "cudgel," also "rude fellow"). Related: Bungled; bungling.
1650s, from bungle (v.).