I'm pretty sure the two names of 'dark matter' and 'dark energy' have caused more confusion than anything else in modern science. They were horrible choices that were worse than even the 'god particle.'

Horrible. Explaining they are placeholders has actually eaten up a fair amount of my time. I'm betting I've probably spent days, if we total the hours up, explaining just that. (I like to go make science simple for people. Having to explain that it is a placeholder doesn't make it easy. So much wasted time.)