Green’s Dictionary of Slang

(Aus.) ‘speedo’-style male bathing trunks.

1993		Aus. Word Map 🌐 sluggers. [...] ‘Growing up in Perth the boys would all be very disparaging about their sluggers or “cock-jocks” and much preferred to swim in footy shorts’.
2007		B.J. Blake Playing with Words 56: Colloquial compounds are often the self-conscious result of attempts at humour, such as some of the recent creations for men’s swimming briefs: cluster busters, nutcrackers, [...] and slug-huggers.
2008		WAtoday.com.au 3 Oct. 🌐 Call ’em cock jocks, sluggos, nylon nasties, budgie smugglers, the banana hammock or the True Test Of Manhood but it breaks my heart to see the way the great Aussie cossie is being scorned by a new generation of beach goers. [Ibid.] About ten, 15 years ago it became ‘weird’, ‘gross’ and ‘creepy’ to bust out the slug huggers.
2012		B. Moore ‘Aus. Sl.’ paper given at Leicester U. Slang Workshop Sept. 2012 n.p.: The speedo variety [of trunks] developed an extraordinary number of risqué or simply curious synonyms: [...] sluggers, sluggos (with allusion to slug meaning ‘penis’), slug huggers.