Mimblewimble (from a post on alt.fan.harry-potter)

[Marco]

No: HPFGUIDX 60815

> As for "Mimblewimble", I wonder... Is it possible that Petunia *is*
a
> squib, but knew about this defense against spells, which info she
then
> passed on to Vernon?  Perhaps this a rare spell that can actually be
> invoked by a Muggle/Squib (as a means of self-defense)...?

unless Vernon has some as-yet-unexplained talent. 

I wonder if this ties into the GoF speech by Dumbledore that states
that 'not even Voldemort' can touch Harry when he's with the
Dursleys... are we absolutely positively sure that Vernon is a muggle
or is it just something we're told? 

I also can't seem to recall the books ever saying that it is possible
for a magical user to easily 'sense' if the other person is a muggle
or not (if it was -that- obvious Harry wouldn't have been surprised
about finding out that Filch is a squib...)

Marco