Yours, Etc.: Origins and Uses of 8 Sign-Offs
"stage direction," 1550s, from Q, which was used 16c., 17c. in stage plays to indicate actors' entrances, probably as an abbreviation of Latin quando "when" (see quandary) or a similar Latin adverb. Shakespeare has it as both Q and cue.
"billiard stick," 1749, variant of queue (n.). Cue ball first recorded 1881.
1928, from cue (n.1). Related: Cued, cueing.