> Why, the same way that "Robert" becomes "Bob" and
> "Richard" becomes "Dick", of course!  It's a mystery to
> me too...

Robert to Bob or Richard to Dick could be explained by bad
handwriting. It would be easy to mis-read R as B, so Bob
rather than Rob, Dick rather than Rick........ Peg via Margaret
-> Meg might also originally have been caused by a mistake

Like the Hebridean island of St Kilda. There is no St Kilda. It
was originally Tobar Childa (or Skeldur in Norse), but corrupted
by English cartographers to S. Kilda. As far fewer people long
ago could write or spell than speak, it's understandable how that
happens

Other hypocoristic (as distinct from nicknames) variations
may be the result of a name passing through other languages
or dialects

I've mentioned this before - I once had to deal with an engineer
called Richard Less, who's parents had either a great sense of
humour (or something a little blacker) or were simply not thinking

Like the woman on TV I saw with the first name La'trene. Sheesh.
Bad as a Boy Named Sue (or Sewer)

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