Green’s Dictionary of Slang

(orig. US) the boss, the leader, anyone senior to or more powerful than the speaker.

1934		T. Minehan Boy and Girl Tramps of America (1976) 171: Maybe this will show some of those goddam bankers and high-ups something to wake them up.
1941		H. Ranfurly diary 16 Nov. in To War With Whitaker (1994) 113: Maybe military high-ups don’t talk and listen enough to the young.
1947		N. Marsh Final Curtain (1958) 131: Chief Inspector? [...] That’d be one of the high-ups, wouldn’t it? Chief Inspector who?
1956		‘Charles Raven’ Und. Nights 96: After a time the high-ups at the Yard got really cross.
1969		T. Murphy Crucial Week in the Life of a Grocer’s Assistant (1978) Scene v: Late for work Monday; later for work Tuesday! That’s the good the high-ups is doing him!
1980		M. Thelwell Harder They Come 201: They [...] cursed the rich, the ‘high-ups’ of society, and the police.
1992		A. Duff One Night Out Stealing 79: Marquess? Ain’t that sumpin hoity-toity high up?
2003		S. Steinberg End of Free Love 77: We say who needs high-ups when lowers have the boardwalk and arcades with songs?
2015		R. Reynolds The Dark Inside 25: I could picture Walters brow-beating McGaffney, flaunting his connections with the high-ups.