Odd words: those that most people don't know

I've often felt that certain ordinary words (either in English or in French) have a curious tendency to remain unknown by people who are not native speakers of the language in question. I shall refer to them simply as odd words. For example, the trivial English adjective "sole" (meaning "only", as in "the sole candidate") appears to be an odd word for many French people who've learnt English at school. I don't necessarily understand why such odd words come into existence.

In everyday French it's easy for me to discover odd words. In most cases, they're French words that I myself have taken ages to know and use. As in English, it's often hard to understand why such and such a word might fall into this category. Here (in my opinion, which might be misguided) is an example:

In the title, I would suspect that "mouise" is an odd word for most English-speaking readers who've learnt French at school. We see that Sarko is in such stuff. But what in fact is it? Well, basically, the journalist is using polite language (?) to say that Sarko, for the moment, is waddling in shit.

This "mouise" term means "gruel" or "porridge", and it probably comes from a Dutch noun akin to "muesli". In our English culture, we all recall that Oliver Twist dared to ask for a second serving of such muck.

I suddenly recall one of my favorite jokes. A slave driver informs his hungry men that he has some good news and some bad news: "The good news is that the chief allows you to survive by eating shit. The bad news is that there won't be enough shit for everybody."