To prevent this, we often ask our Finnish visitors to give us an update on what's going on in the new language. One time it resulted in a hilarious sweat-related conversation which I will relay here.
In the summer, your might sweat so much that dark spots appear in your T-shirt around your armpits. In modern Finnish, these spots are apparently called "policemen" (poliisit).
Then the discussion turned into Finnish sweat-related army slang. It turns out that there are several handy slang words for describing how exactly you are sweating.
kahi - kainalohiki - armpit sweat
pehi - persehiki - ass sweat
muhi - munahiki - dick sweat (*)
pahi - pallihiki - ball sweat
kovahi - kokovartalohiki - full body sweat
(*) Literally, muna means "egg", but it's a slang word for dick. It makes no sense. I am so sorry.
It would be much more logical if egg would refer to testicles, like it does in other languages (for example German). There must have been a linguistic confusion at some point.
The only explanation I have is that the plural "eggs" (munat) means the male genital area in general, and somehow it then happened that the singular then started to mean the most prominent body part in the area.
The upside is that this provides endless amusement for our weekend breakfasts which often involve eggs in one form or another. Every time we come up with at least 3-5 egg-related statements or jokes. It never gets old.