Bathing

google

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Old English bæth, of Germanic origin; related to Dutch bad and German Bad .

wiktionary

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From Middle English bathyng; equivalent to bathe +‎ -ing.

From bath

etymonline

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bathing (n.)

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."