1a. a small firecracker. b. a broken firecracker that burns but does not explode 2a. a brief satirical or witty writing or speech, such as a lampoon b. a short, sometimes humorous piece in a newspaper or magazine, usually used as a filler

I had a hunch that this word, which in the wizarding world of Harry Potter refers to someone born with wizard blood but having no magical powers, might also be a word in the real world of the English language. Maybe J. K. Rowling chose the word because of definition 1b.