>>718335341
Basically 60s spy shit and wartime era stuff. Men were issued sweaters and that carried over into action flicks where they'd wear turtle necks and commando sweaters.
It basically became visual shorthand for "this character is doing sneaky covert shit"

At the same time, catsuits in general were popular fashion so they just naturally melded with the spy craze of the time and it stuck, e.g. the Avengers(the spy show not the Marvel superheroes). Doesn't hurt that women in tight outfits is easy fanservice.