threads is used 175 times,
threading is used 84,
multithreading is used 2679 times.
I would say threads and threading should be merged into multithreading?
On a related note, there's also a bunch of threading-related tags that could be cleaned up a bit. I've done a bunch... but I'm not sure how to retag the question "How does a non-forking web server work?" - it's not using a single existing tag, which seems wrong, but I can't find any suitable replacements..