Green’s Dictionary of Slang

1. to drink down in a single draught, to drink quickly; thus chugger n., a drinker; (US campus) chugging contest n., a drinking competition in which each contestant has to down a succession of drinks in a single swallow.

[1908		Sun. Times (Perth) 10 May 1/1: Even the star of the Thirsty Thirteen couldn’t persuade them [i.e. vaudeville stars the Klos Sisters] to chug-chug [and] a champagne lunch was also foregone].
1968		Frank Zappa ‘The Idiot Bastard Son’ 🎵 I don’t know but I chugged a fifth of White Port once and passed out one day.
1974		(con. 1960s) R. Price Wanderers 27: The guys were getting high, especially Perry, chugging Sevens as fast as he could.
1976		P. Conroy Great Santini (1977) 384: The real warhorse among the contestants drank last; this position of honour was reserved for the best chugger in the squadron.
1976		R. Price Blood Brothers 19: He was chain-smoking and chugging seventy-sevens.
1988		D. Woodrell Muscle for the Wing 46: Bell [...] took a tentative sip of the bourbon, then raised it again and chugged.
1998		D. Hecht Skull Session 181: Damon chugged the beer the barman had set down.
2013		T. Dorsey Riptide Ultra-Glide 117: Serge uncapped a thermos of coffee and chugged.
2019		C. Hammer Silver [ebook] Chugging on his [baby] bottle for a long moment.
2021		J. Ellroy Widespread Panic 97: I chugged Claire’s absinthe.

2. in fig. use, ‘to swallow’.

1991

B. Hamper Rivethead (1992) 132: You would have half the work force breaking their backs and chugging the work load while the other half were off playing cards.