Although all of these words are derived from a common ancestor meaning “hook” and are related to “crook,” they have taken on different meanings in modern English. Those who do needlework with a crochet hook crochet. Your peculiar notions are your crotchets. And a crabby old person like Bob Cratchit’s boss is crotchety. There are various other technical uses for “crotchet,” but people who use them usually know the correct spelling. Just remember that “crochet” goes only with goods made with a crochet hook.