Apparent regression

Around six months or so ago - possibly longer - I converted alll of my
page names to lower case in the interests of standardisation.

Google has just listed 404 errors for perhaps all of these pages using
the old partly upper case spelling. No where on my site - neither in
links or sitemaps - do I still use the old names - and I haven't for
ages.

I can't believe that any other site has links to all these pages - one
or two perhaps. So where has Google got all these old references from?

I'm indexed and ranked well enough for my needs - it's just odd finding
things like this in the stats.