An Etymological Dictionary of Astronomy and Astrophysics

The overflowing of the normal confines of a stream or other body of water, or the accumulation of water over areas that are not normally submerged.

Etymology (EN): O.E. flod “a flowing of water, river, sea,” from P.Gmc. *flothuz (cf. M.Du. vloet, Ger. Flut), from PIE *plo-/*pleu- “flow, float” (cf. Gk. ploein “to float, swim”).

Etymology (PE): Laf “flood,” from Lori, Kordi, Malâyeri, lé in Tabari, variants
lur, lây “flood” [Mo’in, Dehxodâ];
cf. Gk. louein “to wash;” L. luere “to wash;”
Bret. laouer “trough;” PIE *lou- “to wash.” Seyl from Ar.