Cupid is the Roman god of erotic love.
After Parmen had forced Spock and Christine Chapel to kiss, Dionyd warned, "Careful, Mister Spock. Too much love is dangerous," to which Eraclitus added, "Remember, Cupid's arrow kills Vulcans." (TOS: "Plato's Stepchildren")
After Miles O'Brien had managed to bring Rom and Leeta back together again, Julian Bashir rhetorically asked if he should now refer to O'Brien as "Cupid". (DS9: "Ferengi Love Songs")