MM transformed to mm in product explorer

this is not a big problem but it is definitely weird so I thought I would report it.

I have a child category called MM. it appears as MM in mysql and appears as MM in front end (as far as I can tell so far anyway) but is transformed to mm in backend category/product explorer. I even renamed it, let it be for a few days, and then renamed it XX (which shows in capital XX letters in prod/cat explorer) then back to MM after a few logouts and computer reboots and there it is as mm still. weird.

it's not a problem for me necessarily since it seems to be appearing properly in front end but I find it very odd, cannot figure out why it is happening and want you to know about it in case it might signify some other issue.