Best explanation of what KERNEL is, it's like car engine and all electronics around it. It's all hidden under the hood, but makes the whole thing run.

Cars have been around for long enough that even non techy people understand at least the crudest basics and this helps them understand computer things when used as analogy.

It's a government agency in the United Kingdom called the Ordnance Survey. They make all the maps.

I was originally set up to help defend against catholic rebellions so it is historically linked to the army. That's probably where the Colonel comes in to it.