hair on one’s chest n.
an emblem of masculinity; in phrs. below.
[20C+] to be brave, to be plucky (cf. have a (wild) hair up one’s ass under hair n.).
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.
[late 19C+] (Aus.) a general excl. of approval, acclamation, ‘good for you!’, ‘well done!’ etc.