Why is the ninth month called September?
13c., from Old English dufan "to dive, duck, sink" (intransitive, class II strong verb; past tense deaf, past participle dofen) and dyfan "to dip, submerge" (weak, transitive), from Proto-Germanic *dubijanan, from PIE *dheub- (see deep). Past tense dove is a later formation, perhaps on analogy of drive/drove. Related: Diving. Dive bomber attested by 1939.
c.1700, from dive (v.). Sense of "disreputable bar" is first recorded American English 1871, perhaps because they were usually in basements, and going into one was both a literal and figurative "diving."
: They fixed it so that he'd dive in the fourthRelated Terms
[origin of first sense uncertain; perhaps fr the notion that one could dive into a disreputable cellar haunt (called a diving bell in an 1883 glossary) and lose oneself among lowlifes and criminals; perhaps a shortening of divan, ''a smoking and gaming room,'' a usage popular in London in the mid-and late 19th century; the places were so called because they were furnished with divans, ''lounges,'' the name ultimately fr Turkish]