Green’s Dictionary of Slang

(orig. US) that’s mine! I want to do that! I want a share! A child’s term used to claim the whole or an equal part of an object; the negative response to the cry is fen dibs.

1932		L.W. Merryweather ‘Argot of an Orphans’ Home’ in AS VII:6 401: Dibs on that magazine when you’re through.
1953		L. Uris Battle Cry (1964) 186: Dibs on your beer, Mary.
1960, 1975		Wentworth & Flexner DAS.
1989		P. Munro Sl. U. 170: Shotgun! [...] Dibs on the front passenger seat!
1996		P. Beatty White Boy Shuffle 224: Ignoring the Japnese claim of dibs to the bomb as a keepsake of war.
2001		OnLine Dict. of Playground Sl. 🌐 dibs n. Shouting this word is laying claim to something; the last cookie, the best seat, the right to go first in a game.
2015		S. King Finders Keepers (2016) 45: Tina’s got dibs on the Rolls for her tennis lesson at the country club.
2019		M. Herron Joe Country [ebook] ‘[I]f you have any big psychological block about shooting your father, I’ve got dibs’.