Green’s Dictionary of Slang

(US) a general statement of contempt or dismissal.

1889		in Kansas Hist Quarterly XIII (1944) 128: Murphy, k.m.a [HDAS].
1922		Joyce Ulysses 140: K.M.A – Will you tell him he can kiss my arse? Myles Crawford said, throwing out his arm for emphasis. [Ibid.] K.M.R.I.A. – He can kiss my royal Irish arse.
1941		R. Sykes [song title] K.M.A. BLues.
1988		Running Wild ‘Prisoner of Our Time’ 🎵 Living life / My own way / Not tomorrow, but today / You are against me, but I tell you K.M.A.!!!
2005		www.greeneyedmonster.net 🌐 After that, hopefully I can tell the Crack House to KMA, give my two weeks notice, and start my 2–3 week vacation before I report to my new job.