Here is what I have concluded is the definitive 'actual' story about the name, based on reading many things over many years and knowing many people: The name came about when Jeff Beck, Jimmy Page, JPJ and Keith Moon recorded "Beck's Bolero". Apparently, everybody was so turned on by the session that they were seriously considering forming a band with this line up. Keith was obviously a member of the Who at the time, and he commented that him leaving the Who, which he was very tempted to do, 'would go over like a lead zeppelin', so they might as well name the band that. It was never a comment about how the band now known as LZ would fare, as many accounts depict. The name Lead Zeppelin sat around for a while and then was eventually chosen as the name for the band after they did some Scandinavian gigs under the moniker in question. The "a" was dropped so that the punters wouldn't pronounce it 'leed'.
Other than that, this question is too easy. How about, can anybody tell me who the songwriting duo of Nanker and Phelge are?