Green’s Dictionary of Slang

1. a shout; also as v., to speak.

1894		Civil & Milit. Gaz. (Lahore) 18 Oct. 4/3: While the padre ’e bolos the ’ukm, / An’ yer chums give the stiffun’s salute!
1943		R. Llewellyn None But the Lonely Heart 337: Can’t call in on the Lord Mayor, but we’ll give the old bleeder a bolo when we go by his house. Perhaps if he ain’t in kip, he might lean out the bedroom window and give us the time of day.
1971		(con. WWII) B. Aldiss Soldier Erect 43: You lot want to bolo the bhat a thora, you do!

2. (US) a form of unorthodox chopping punch.

1953		‘John Eagle’ Hoodlums (2021) 36: Martin was a sucker for a feint to the stomach and a looping hook, maybe a bolo punch.
1954		Joplin Globe (MO) 20 Oct. 9/1: A resourceful puncher with [...] a fancy eyecatching bolo right.
1963		‘Jay Solo’ ‘A Girl Named Poison’ in Pulling a Train’ (2012) [ebook] Harry took ten quick steps to him and bolo-punched him full in the stomach.
1971		E. Bullins ‘Dandy’ in King Black Short Story Anthol. (1972) 68: A mighty dig to the gut with a boloed right. [Ibid.] 69: Stevie finally creamed the shadow to the sidewalk with a left bolo to the kidneys.