It’s not just the tango that’s complicated or misleading: Scottish music is apparently prey to the same terminological confusion. Writing about naming conventions in collections of dance tunes dating back to the 18th century, Pat Ballantyne writes:
What to us is clearly a strathspey, with its jerky, dotted rhythms, might be called a reel. What to us is a reel, with a constant, even rhythm, is sometimes called a jig. In the eighteenth century in particular, the names for different types of dance music were interchangeable.
The source for this is a page about the background to the James Scott Skinner collection at the University of Aberedeen. Take a look: it’s got digitized fiddler’s books and dance manuals, audio clips of Skinner playing, video clips of Scottish ballroom dances, links to other sites, and fascinating potted histories. Wonderful.