Old English wæter, from Proto-Germanic *watr- (source also of Old Saxon watar, Old Frisian wetir, Dutch water, Old High German wazzar, German Wasser, Old Norse vatn, Gothic wato "water"), from PIE *wod-or, suffixed form of root *wed- (1) "water; wet."
To keep (one's) head above water in the figurative sense is recorded from 1742. Water cooler is recorded from 1846; water polo from 1884; water torture from 1928. Linguists believe PIE had two root words for water: *ap- and *wed-. The first (preserved in Sanskrit apah as well as Punjab and julep) was "animate," referring to water as a living force; the latter referred to it as an inanimate substance. The same probably was true of fire (n.).
common name for a plant of the mustard family, Old English cresse, originally cærse, from Proto-Germanic *krasjon- (source also of Middle Low German kerse, karse; Middle Dutch kersse; Old High German kresso, German Kresse), from PIE root *gras- "to devour" (see gastric). It underwent a metathesis similar to that of grass. French cresson, Italian crescione are Germanic loan-words.
Others are reading
<a href="https://www.etymonline.com/word/watercress">Etymology of watercress by etymonline</a>
Harper, D. (n.d.). Etymology of watercress. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/watercress