1) naming things
2) cache invalidation
3) off-by-one errors
It was, I'm sure, named hastily while they were in the earliest stages of development, thinking primarily about what the code would do and not much about what to name it. Renaming things later was never the highest priority, and then eventually far too much was built on it to change things.
The problem is, if you actually spend a lot of time at the beginning thinking about the name, you may not do much better, because software architecture often turns out to be somewhat different than the original plan. Naming things at the beginning fails for the same reason detailed product specs at the beginning often fails, but unlike functionality, names are rarely changed later once the situation is better understood.