Green’s Dictionary of Slang

(orig. US) of a child or adolescent: spoiled, badly-behaved; of an adult: immature, given to behaving like a spoiled child.

1907		L.A. Times 13 Oct. 29/3: The villain, much to the relief of the audience, kills a most objectionable ‘bratty’ little white boy.
1921		Pittsburgh Dly Post (PA) 21 Aug. 12/2: You remember that bratty little Elmer Doolittle [...] The measley little redhead with the freckles.
1934		Herald (Crystal Lake, IL) 1 Mar. 1/2: Bratty little Oliver tate, shooting spit-balls at the kids in the front rows.
1940		Vidette-Messenger (Valparaiso, IN) 14 Feb. 3/4: She is [...] the sort of child who will be taken into the hearts of chidlren and adults alike because she’s not ‘bratty’ and doesn’t trot out ability to sing or tap dance [...] at the slightest provocation .
1961		in Webster III.
1971		J. Mandelkau Buttons 104: He sounded like a bratty kid who gets mad at another kid riding his bike.
1981		Eble Campus Sl. Mar. 5: punk – bratty, sloppy, mean kid.
1999		T. Dorsey Florida Roadkill 98: You were sick of all the snooty moms and their bratty little shits.
2010		Codella and Bennett Alphaville (2011) 248: The guy just shook his head like a bratty kid.