1.A literal meaning is a pair of underpants.
2.Substitute for "asshole, dickweed, fuckball, fucktard, bitch, bastard, asskisser, donkey-raping shit eater, shit face, etc."
3.The cool way of saying asshat(see above descriptions)
1."Are you wearing your 455H47?"
2."God what an 455H47."
3."You're a real 455H47."