I have just had a short discussion with somebody online about how some scientific terms are hugely misleading due to some historical misunderstanding. The example that I put forward was the term 'planetary nebula', which was originally given to objects that looked like planets in poor quality 18th century telescopes. We now know that they are gas clouds around old dying stars, and have nothing to do with planets. This caused me to make a fool of myself once when I gave a talk as an undergraduate. I got the idea from this conversation to ask people on this website if they know of other great examples like this one. Maybe we can make a good list of hilariously silly scientific terms that could probably do with being renamed. Come on guys, lets see what you've got.