Green’s Dictionary of Slang

(US) a fantasy world; thus in la-la land, out of touch with reality, drugged or drunk; also attrib.; laa-laa adj., mad.

1969		N.T. Rosenberg California Angel 34: Pointing an assault rifle at someone isn’t negative? Give me a break, Toy. You live in la-la land. This is a war zone here.
1979		L.A. Times 28 July II3/4: Heather was in la-la land after taking a dose of her own medicine by drinking the LSD-spiked iced tea intended for Diana.
1991		Eble Campus Sl. Fall.
1999		Guardian Rev. 17 July 12: Media studies, useful for a job in TV ? You must be laa-laa.
2000		N. Barlay Crumple Zone 200: A real place. Not fuckin’ la la wha’ever land.
2000		Indep. Rev. 17 Feb. 10: My expectations of having a 9–5 job belonged in La-La Land. Shifts here are just as likely to be 3pm–11pm.
2000		Indep. Rev. 7 Apr. 11: Grace begins as a la-la land version of Pinocchio.
2003		McGill Reed Dict. of N.Z. Sl. 125: la-la land Bemused zone where somebody drugged or boozed or heavily tackled resides.
2013		D. Copperfield [bk title] Wasting More Police Time: Further Adventures in La-La Land.
2015		Guardian CiF 10 Sept. 🌐 What The Guardian and its army of lala land columnists would want us to do is [...] admit hundreds of thousands (if not millions) of economic migrants.
2024		K. Noem No Going Back 177: [U]nless we give them a dose of our realities, they’ll stay in la-la land.