1890, New Englandish word for "swimming pool," from Latin natator "swimmer" (from nare "to swim") + -ium, neuter suffix. Latin nare is from PIE root *sna- "to swim" (cognates: Sanskrit snati "bathes;" Avestan snayeite "washes, cleans;" Armenian nay "wet, liquid," Greek notios "wet, damp," nekhein "to swim;" Middle Irish snaim "I swim," snam "a swimming"). Middle English had natatorie "a pool, bath," early 14c., from Latin.