cue (n.1)

"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" (from PIE root *kwo-, stem of relative and interrogative pronouns) or a similar Latin adverb. Shakespeare's printed texts have it as both Q and cue.

cue (n.2)

"billiard stick," 1749, variant of queue (n.). Cue ball first recorded 1881.

cue (v.)

1928, from cue (n.1). Related: Cued, cueing.