1550s, "act or process by which organisms absorb their proper food into their systems and build it into living tissue," from Old French nutrition (14c.) and directly from Latin nutritionem (nominative nutritio) "a nourishing," noun of action from past-participle stem of nutrire "to nourish, suckle, feed," from PIE *nu-tri-, suffixed form (with feminine agent suffix) of *(s)nau- "to swim, flow, let flow," hence "to suckle," extended form of root *sna- "to swim." Meaning "that which nourishes, nutriment" is from c. 1600. Related: Nutritional.
It forms all or part of: naiad; natant; natation; natatorial; natatorium; nekton; nourish; nurse; nursery; nurture; nutrient; nutriment; nutrition; nutritious; nutritive; supernatant.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit snati "bathes," snauti "she drips, gives milk;" Avestan snayeite "washes, cleans;" Armenian nay "wet, liquid;" Greek notios "wet, damp," Greek nan "I flow," nekhein "to swim;" Latin nare "to swim," natator "swimmer;" Middle Irish snaim "I swim," snam "a swimming."