Mary Fisher wrote:

I'm interested in the origin - but not enough to press you if you don't
divulge such things :-)

Oh, it's come up here before now, I think. 'S Polish: Stefek is 'Steve'
(the formal one's 'Stefan' = Ste(ph|v)en); Zaba - we write it with a dot
over the Z in the Olde Countree, making it a harsh sound wot doesn't
occur in English but is least dissimilar to the 'dr' in 'children' -
means Frog. Never know when that mightn't come up in Trivial Pursuit, as
I usually go on to say...

Stefek