cue (n.2) Look up cue at Dictionary.com
"billiard stick," 1749, variant of queue (n.). Cue ball first recorded 1881.
cue (v.) Look up cue at Dictionary.com
1928, from cue (n.1). Related: Cued, cueing.
cue (n.1) Look up cue at Dictionary.com
"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.