Green’s Dictionary of Slang

hair on one’s chest n.

an emblem of masculinity; in phrs. below.

In phrases

put hair(s) on one’s chest (v.) (also grow hairs on one’s chest)

1. [1910s+] to embolden, to make stronger, usu. used of sex, food, drink.

2. [1940s] to cheer up, to strengthen; esp. in context of offering a drink, e.g. that’ll put hair on your chest.

In exclamations

more hair on your chest!

[late 19C+] (Aus.) a general excl. of approval, acclamation, ‘good for you!’, ‘well done!’ etc.