If you haven’t seen it yet, America’s Secret Slang, which is produced by the History Channel, is worth checking out. There are currently 9 episodes available, most of which are 44 minutes long.
I happened to catch this show one day when I was channel surfing and quickly got sucked in. I haven’t seen all of the episodes, but I’ve been impressed by what I’ve seen. Each episode takes on a general theme and then examines the origin of slang (including idioms) that relate. Most of the segments include a person-on-the-street segment asking native speakers if they use a slang term (spoiler: they do) and if they know its origin (they usually don’t, but they often try making one up.) The origin and explanation is then revealed through in an interesting and visual way including animated words and historical re-enactments.
I’ve linked to one episode, above, and the rest are available on the History Channel website and YouTube. Be aware the the show is rated PG, so you may want to preview episodes before watching them in class or assigning them to your students. Non-native speakers will appreciate being able to rewind and review the videos online. They can also turn on captions if they find that helpful. Overall, the shows are very well made, include a ton of information, and are interesting to native and non-native speakers alike.