I noticed that a search for what's a bell end on Google brings up this site at number one, so I thought I better answer the question.
So here goes, bell end refers to the end of a man's, er, manhood. The name came about because it's shaped somewhat like a bell (go on have a quick check, nobody's looking) and it is, in fact, the end. It's a simple as that, although it's often used as something of a derogatory term, where someone might say "he's such a bell end".
The obvious follow on question is why on earth I chose it as my blog name? And the answer to that is I'm not entirely sure. I've certainly been called it quite a few times (due to the surname) and couldn't think of anything more appropriate at the time.