A chaperone was a person who accompanied another person to prevent inappropriate behavior. When T'Pol joined the crew of Enterprise NX-01 in 2151, Admiral Forrest suggested they think of her as more of a chaperone, not a Vulcan spy as Trip Tucker originally called her. (ENT: "Broken Bow") Data was chosen as Kamala's chaperone in 2368 as he was immune to the effects of the Finiis'ral, having no emotions. (TNG: "The Perfect Mate" )