More recently we've come up with another term.
The term is Knowhole.
It is defined as an odd hole in a person’s knowledge that would be considered in general to be common knowledge.
An example would be not knowing that unicorns had horns.
It evolved from the term Noah hole, for a co-op on my team who didn’t know that unicorns had horns.
The usage has expanded. Here are some practical usages that I’ve heard:
You’ve never heard of the Ukraine? That’s a pretty big knowhole.
Shove this in your knowhole.
Take this book and stick it in your knowhole.
English is a beautiful language, let's help it blossom and grow.