A term coined by the uberpopular podcast - Keith and the Girl. Refering to when a fan of their show wears one of their t-shirts on Wednesday, they are supposed to get a blow job from friends or strangers.
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!"