When someone's socks are rolled down near their ankles, forming what unequivocally reminds you of a new condom, you say that the person is wearing Trojan socks...
Dude 1: "Look at that cute girl going into the gym"
Dude 2: "Too bad she's wearing Trojan socks..."
Dude 1: "True! She looks like out of the 80's!"