Worked with some royal marines a few years back and it’s a nickname that all marines of all countries are called or so I was told.
Mud stompers, grunts, crunchies, duckfeet, bullet sponge, waffle makers (not sure where this one came from, I thought they were boots,) death from the sea, legs (or so says the Airborne HA,) human pack animals, gun toten sea apes, etc…..
I just picked the less harsh sounding one.