When you're going down on a woman ( preforming cunnilingus ) and she clamps her thighs on your head covering your ears, cause you're doing such a good job on your prefomance.
Peter was very sad that he had not seen the ocean in a while. He decided to ask two of his friends to give him German Earmuffs so he could at least hear it.
"Earmuffs" is a term to describe a girl that has amazingly sexy thighs that you want wrapped around your head. That way you can eat her muff while your ears are covered. Hence, being Earmuffed.