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."
Entries linking to bathing
bathe v.
Middle English bathen, from Old English baþian "to wash, lave, place in a bath, take a bath" (transitive and intransitive), from the source of bath (q.v.), with different vowel sound due to i-mutation. Related: Bathed; bathing. Similar verbs in Old Norse baða, Old High German badon, German baden.