perspiration (n.) Look up perspiration at Dictionary.com
1610s, from French perspiration (1560s), noun of action from perspirer "perspire," from Latin perspirare "blow or breathe constantly," from per "through" (from PIE root *per- (1) "forward," hence "through") + spirare "to breathe, blow" (see spirit (n.)). Applied to excretion of invisible moistures through the skin (1620s), hence used as a euphemism for "sweat" from 1725.