Green’s Dictionary of Slang

(UK juv.) that’s mine! I want to do that!; an allied formula, mainly in preparatory schools, is quis? (Lat. who?) to offer an object, to which the responses are ego! (Lat. I) if one wishes to make a claim, or baggy/bags I no par (no part) if one wishes to be excluded.

1887		‘A Plain Woman’ Poor Nellie I 110: ‘But hang it!,’ he laughed, ‘slang or not slang, bags I Nellie!’.
1909		Gem 6 Feb. 27: Bags! I’ll have that big chestnut.
1913		C. Mackenzie Sinister Street I 103: He could shout [...] ‘bags I’ to secure an advantage.
1926		Kipling ‘Propagation of Knowledge’ in Complete Stalky & Co. (1987) 229: Bags I the dyin’ tree, then.
1945		(con. 1937) R. Westerby Mad in Pursuit 189: ‘Bags I,’ they said.
1946		(con. 1912) B. Marshall George Brown’s Schooldays 51: Bags I not ring the bell.
1950		A. Buckeridge Jennings Goes To School 44: No, bags I walk with the limp.
1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 215: ‘Bagsy’, ‘Baggy mine’, and ‘I bags it’.
1965		R. Stow Merry-Go-Round in the Sea 76: ‘I bags going in the transport,’ he shouted.
1968		P. Terson Apprentices (1970) I i: Bags I last to clock on.
1976		D. Ireland Glass Canoe (1982) 103: Bags first shot.
1981		Weekend Australian Mag. 7-8 Mar. 4: Someone must tell him the only thing wrong with Gunston’s Australia is Gunston. Bags you do it.
1989		A. Ahlberg Heard it in the Playground (1991) 30: Bags I the dummy / Bags I the cot / Bags I the rubber duck / That other baby’s got.
1997		Roger’s Profanisaurus in Viz 87 Dec. n.p.: guard’s van n. Of pulling a train (qv), the least desirable position in the queue. As in: ‘Bagsy I’m not in the guard’s van fellas’.
2000		N. Griffiths Grits 143: Bagsy ferst shot on the syringe!
2001		OnLine Dict. of Playground Sl. 🌐 bags n. [...] 2) a claim of ownership, e.g. ‘Bags I that cake!’.
2005		C. Hopkins Mates, Dates and Great Escapes 91: ‘Bagsy the top,’ I said as I slung my rucksack on the top bunk.