Irma Pince is Snape's mother in disguise? AND Filch Squib or Muggle??? then.

[rt11guru]

No: HPFGUIDX 137273


Potioncat:
<Snip>
No I think JKR chose the name Pince for the library fine of "a >
pence", although I've long ago forgotten where I first heard that 
idea. 

Guru:

It could also come from pince-nez, spectacles with out ear pieces that
are held on by pinching your nez (nose).  An appropriate name for a
schoolmarmish character.


As far as Filch, I haven't seen anyone put forth the opinion that he
might be the one who comes to magic late in life.  He's a squib, he's
been around Hogwarts enough to have picked up knowledge of spells,
charms, and hexs. Sort of the "Good Will Hunting" of Hogwarts.





Guru