nutrient (n.)

"a nutritious substance," 1828, noun use of adjective (1640s) meaning "providing nourishment," which is from Latin nutrientem (nominative nutriens), present participle 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."