Note: This post contains discussion of the human body and genitalia. I'll try not to gross you out too much, but proceed at your own caution!
Moikka! My Finnish teacher recommended your awesome blog and it indeed seems terribly useful, so thank you for writing it! I also have a question, I've come across the word munaskuu lately and looking it up in several dictionaries I've become quite confused about how exactly it's used. it seems like the translations ranged from guts (like in gut feeling) to kidney and testis. are all of these correct? also, I haven't really found a good translation for mennä puihin, could you help me out with that? thanks a bunch in advance and also for your great work with the blog!
Thank you for your kind words and really interesting questions! I'll start with the first one and save "mennä puihin" for another post, so this one doesn't become much too long.
You've got the general meaning right: munaskuu can refer to vague anatomy, hence the translations kidney and testis. Munaskuu doesn't directly refer to the gut, but that's also one possible translation. In English you'd say that you feel something in your gut, but in Finnish you could say that you feel it in your kidneys, tunnen sen munaskuissani. However, it's much more common to feel something in your gut in English than it is to feel something in your kidneys in Finnish.
The original meaning of the word seems to be 'kidney', but to me personally the primary meaning is definitely 'testis' or 'testicle', and a quick google search reveals that this is not just a personal quirk of mine. Before receiving your question, I thought that the standard written form of the word was munasku, with just one u, and this form yields a lot more male genitalia than munaskuu on google. You've been warned!
When I look at the search results for munasku and munaskuu, I'm also no longer that confident that munasku and munaskuu are even the same word - I mean, they certainly come from the same origins, but they're written differently and seem to have surprisingly different meanings. Munaskuu, according to Institute for the Languages of Finland, is definitely kidney and invokes biblical and generally old fashioned literary connotations. The first written instances are from Agricola. Munasku, on the other hand, primarily seems to mean testis and is much more vulgar - maybe old fashioned, also, but not in a high brow let alone biblical way. It's more like something that an older man might say while drinking Koskenkorva by the wood pile (a time honored Finnish tradition).