Why is the ninth month called September?
late 15c., "to divert the attention, beguile, delude," from Middle French amuser "divert, cause to muse," from a "at, to" (but here probably a causal prefix) + muser "ponder, stare fixedly" (see muse (v.)). Sense of "divert from serious business, tickle the fancy of" is recorded from 1630s, but through 18c. the primary meaning was "deceive, cheat" by first occupying the attention. Bemuse retains more of the original meaning. Related: Amused; amusing.