I think we all understand why git branches are called branches, the problem is that it's a misleading name.
Git branches are pointers to commits. For example I can move the pointer to a commit to point to the previous commit instead. But the commit which was previously being pointed to is still there. However when I say that I reset a branch to a previous commit, I get the feeling that the branch was "cut", and so that the commit was lost - which is not the case.
This is why using the name "bookmark" is better in my opinion. Not because I'm used to it (I've used git much more than mercurial), but because it's a better representation of what is actually happening.
For all intents and purposes, as long as no other branch is pointing to that commit, that commit is 'lost'. It's not immediately removed from your hard drive, but it's no longer considered part of your history.
Note that the technical name for branches in git is refs or references, which more accurately describe their nature.
Git branches are pointers to commits. For example I can move the pointer to a commit to point to the previous commit instead. But the commit which was previously being pointed to is still there. However when I say that I reset a branch to a previous commit, I get the feeling that the branch was "cut", and so that the commit was lost - which is not the case.
This is why using the name "bookmark" is better in my opinion. Not because I'm used to it (I've used git much more than mercurial), but because it's a better representation of what is actually happening.