Many British army regiments have, or had, nicknames of this sort, based either on some historical event or on some idiosyncrasy of their uniforms. The marching song is a famous old tongue-twister: “I’m not a pheasant plucker, I’m a pheasant plucker’s mate/ I’m only plucking pheasants since the pheasant plucker’s late.” (Another variant substitutes “son/come” for “mate/late”.)