I could indeed give some explanations but I fear they won't be as exhaustive as in the RFC 3092.

A LOT of french coders use toto (and its phonetic derivatives tata,tutu,titi).

'toto' has always been used as common name, in school
('toto is riding a bicyle a 10 mph, how long will it take to makes 25 miles ?')
or in common life where it's used in joke and examples.

It's part of our culture, just as I suppose you (english/american ?) use 'joe'.

The laziness factor is also inportant as 'toto' is even faster to type than 'azerty'(our 'qwerty') or '1234'.

"Only Bad Coders Badly Code In Perl" (OBC2IP)