I don;t think that is so unusual.
I write for a living and I consider myself above average in terms of being well-read, and it's a term I have never heard of - but then, it's hardly something that crops up in everyday conversation is it?
Hand on heart - without looking it up - do you know what an Alnager* does?
And again - if you live outside this area, you wouldn't know what a
Sagger Maker's Bottom Knocker
does - but if you asked ten people over the age of sixty in my town, nine of them could tell you.
It's just about what you come across in your life, it's no indication of intelligence - or qualification to teach.
* It's a Wool Inspector.