How Does James know Levicorpus?

Snape creates a number of spells as the Half Blood Prince, but we also see James use them too, especially the Levicorpus spell. How do you think James knows that spell? Do you think he saw Snape use it once and decided to copy it, if so, who did snape use it on? Or maybe James stole his potions book, as a prank, and got some spells from there?