I think you mean, "Set laew" (high tone on the laew, "lae" as in lad, "w" as in cow. It sounds like the word low, as in the sound cows make, except replace the o with the a from lad).
Normally when used, it means "I'm done," or "I'm finished." But when you are having sex, it means, "I came." Literally, the words mean "finished already."