Italian muscle 

When speaking of one's Italian muscle, one often refers to the male genitalia also referred to as 'phallus'. Due to the Italian culture often being associated with romance and affection, and the penis being a prominent muscle, one's "Italian muscle" is a reference to one's penis.

"He really knows how to flex his Italian muscle"
"I could use some Italian muscle on Friday night"

Italian muscle by Michelangelo November 29, 2021