"Monkey nuts" also shows up in the halyard chantey "Serafina" which is about a Spanish prostitute of that name. The line where it is mentioned is: "She used to work for monkey nuts but now she works for vino." It can be found in Stan Hugill's Shanties From The Seven Seas. He doesn't give an explanation of the phrase, but reading the message above about it being a British Isles slang expression for peanuts puts it in perspective. That might be what is meant in the chantey. That's conjecture, but it makes sense.