A discarded napkin already used by a bum/tramp/dero in McDonalds. For it to qualify as a trampkin, you have to use it to clean your hands or mouth by mistake (or on purpose).
That's not mine... it belonged to that bum who was sitting across the table. Gross, you just used a trampkin on your face!!
Jeez, Heidi, you let me use that stank trampkin without saying anything!