Green’s Dictionary of Slang

to wash oneself (in a bath or tub).

1650		News from the New-Exchange (1731) 11: Item, for fluxing, fuming, soaking and tubbing of H--, a worthy Member; yet all will do no Good.
1610		Jonson Alchemist IV i: In your bathada, You shall be soked, and stroked, and tubb’d, and rubb’d, And scrubb’d, and fubb’d, dear don.
1731		News from the New-Exchange (2 edn) [as 1650].
1883		Illus. London News 27 Jan. 87/3: To ‘tub’ for to bathe is [...] Society slang (generally and university).
1885		Bulletin (Sydney) 9 May 12/1: One thing is certain – that if the alderman don’t tub until their drought has subsided, not a man Jack of them will ablute till the Day of Judgment.
1890		Bird o’ Freedom 1 Jan. 1/1: People who live in glass houses should have curtains — especially when they are tubbing.
1927		W.R. Morse ‘Stanford Expressions’ in AS II:6 278: tub — plunge into a tub of cold water.
1929		Bulletin 13 Nov. (Red Page) 5: Why any nation would pride itself on being ‘well tubbed’ is a mystery.
1974		D. Ireland Burn 123: The smell of her. Dark. Just won’t tub.
1988		‘Siriusly’ Speaking in Just Us (H.M. Prison, Beechworth, Vic.) Dec. 26/2: non-tubbern.One who does not shower, unhygenic person.
1990		Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Tub. To shower or bathe. As in ‘to have a tub.’.