“Cully” can be used as both a noun (“the tricked”) and a verb (“to trick”). The first usage in the mid-17th century was the noun, meaning “one easily tricked or imposed on,” but its modern usage is slang meaning “companion, mate.” While we wouldn’t consider it very good form to swindle your friends, you might pull a prank on your pal — or, in other words, cully a cully.