Nope, no glass of water. It was a phone interview. I'm sure I was better than I imagined, at least I hope so. I only messed up in the very beginning when I froze, but it got easier after that.
I don't have a transcript, but this is what I mentioned:
Bob and Bill are similar in that (1) they are both shorter than the original names, which was done simply because they are familiar forms and it makes them easier to say, and (2) they both start with a different sound than the original name.
There are various theories as to why this came about, and these theories could have worked in combination with each other. The distribution of names was thinner in the Middle Ages, so many people would share one name, creating a need to distinguish one Robert from another. There were several other rhyming nicknames for Rob, eg Hob, Nob, Dob, (which gave rise to surnames such as Hobbes and Hobson) but they have all died out now. I gave other examples of rhyming nicknames such as Meg and Peg, and Ed, Ned, and Ted.
At this point the interviewer, Sheila Coles, made a joke about Hob's your uncle. She asked me about other diminutives, so I brought up Dick and Richard, and mentioned how the pronunciation of the trilled Norman 'R' may have presented problems to the Anglo-Saxons causing them to substitute a 'D' sound (as mentioned in Hanks'n'Hodges). I also mentioned that Bill may have come about because of difficulty Gaelic speakers may have had with the 'W' sound.
She wrapped it up at this point and mentioned she'd like to have me back sometime. The whole thing lasted only a couple minutes (or so it seemed).