Green’s Dictionary of Slang

(UK juv.) the buttocks, us. a baby’s or small child’s .

1873		Sl. Dict. 94: Botty, [...] an infant’s posterior. Nursery.
1907		C. Prendergast Sadopaideia 18: Let’s look at the poor little bottie. Turn round, is it much cut up?
1922		Joyce Ulysses 724: Grinning all over his big Dolly face like a well-whipped childs botty.
1975		D. Nobbs Fall and Rise of Reginald Perrin (1976) 33: ‘Wet botty,’ said Adam.
1982		N. Keesing Lily on the Dustbin 25: Many people listed ‘bottom’ as a genteelism, but gave ‘bum’ as its synonym implying that ‘bottie’ was the politer word.
1999		Observer 24 Oct. 29: Claire Short gets her botty publicly smacked.
2006		E. St Aubyn Mothers Milk 11: I’ve changed His Majesty’s nappy so he’ll have a nice dry botty.
2012		Slate 20 Jan. 🌐 While I try desperately to catch a glimpse of Mick’s bottie, my pals focus on the chests of the two ladies.
2021		P Howard Braywatch 36: ‘We got each utter’s nayums tattooed on eer botties as a soyun of eer lub for each utter’.
2023		R. Milward Man-Eating Typewriter 90: I landed at the bottom step [...] bruising my botty.