watermelon n.

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.).

late 14c., meloun, "herbaceous, succulent trailing annual plant," or its sweet, edible fruit, from Old French melon (13c.) and directly from Medieval Latin melonem (nominative melo), from Latin melopeponem, a kind of pumpkin, from Greek mēlopepon "gourd-apple" (name for several kinds of gourds bearing sweet fruit), from mēlon "apple" (see malic) + pepon, a kind of gourd, which is probably a noun use of pepon "ripe" (see pumpkin).

Among the earliest plants to be domesticated. In Greek, melon was used in a generic way for all foreign fruits (compare similar use of apple). The Greek plural of "melon" was used from ancient times for "a girl's breasts."