bathe v.

Old English bæð "an immersing of the body in water, mud, etc.," also "a quantity of water, etc., for bathing," from Proto-Germanic *badan (source also of Old Frisian beth, Old Saxon bath, Old Norse bað, Middle Dutch bat, German Bad), from PIE root *bhē- "to warm" + *-thuz, Germanic suffix indicating "act, process, condition" (as in birth, death). The etymological sense is of heating, not immersing.

The city in Somerset, England (Old English Baðun) was so called from its hot springs. Bath salts is attested from 1875 (Dr. Julius Braun, "On the Curative Effects of Baths and Waters"). Bath-house is from 1705; bath-towel is from 1958.

1540s, verbal noun from bathe (v.). Bathing suit is recorded from 1852 (bathing costume from 1830); bathing beauty is from 1891, in reference to Frederick Leighton's "The Bath of Venus."

late 14c., basken "to wallow" (especially in warm water or blood, of unknown etymology. The Middle English Compendium rejects the derivation from Old Norse baðask "to bathe oneself" (with loss of middle syllable), reflexive of baða "bathe" (see bathe) + Proto-Germanic *-sik "one's self" (source also of German sich; see -sk).

The meaning "soak up a flood of warmth" is apparently due to Shakespeare's use of the word in reference to sunshine in "As You Like It" (1600). Related: Basked; basking.