What is humming slang for?

Humming slang is a type of secret language used primarily by British criminals to communicate with each other discreetly. It involves replacing certain words with unrelated rhyming words or phrases. The purpose of humming slang is to confuse or hide the true meaning of conversations from outsiders, such as police or authorities. For example, instead of saying face, a person using humming slang might say boat race. So, if a criminal wanted to discuss a robbery, they may say Let's plan a few sweet apples instead of openly talking about a robbery. This use of rhyming slang allows criminals to speak more freely without others understanding their true intentions.