In my hometown, we called it a "dog chain." A length of heavy chain, motorcycle chain, or wire cable about the length of your arm, used to beat somebody senseless. It's most accurate D&D analog is a flail: you hold both ends in one hand to make a loop, and you start swinging. Comic books and action movies show people twirling them around and doing amazing stuff with them, like disarming their opponent or tripping them, etc., but it never happens outside of the realm of make-believe.
Which is fine for most people, since D&D is a game of make-believe. That's why I said that I didn't have a problem with them being in the game; they are perfect in the context of a comic-book action style of play. It's just not something I go for.