I've became interested in etymology and have a lot of fun little facts to share.
Disclaimer that I'm not a linguist and I'm just someone who read too many wiktionary entries
My native language is Russian, and I'm slowly learning some Polish - so the rambles are going to be about these two, or sometimes also about English and its relatives.
- Proto-Slavic had a word "*praščurъ", which meant "ancestor". Both Russian and Polish retained this word in the same meaning - "пращур"/"praszczur", but in Polish the word is pretty antiquated.
The fun comes from under the floor (where the rats live) - the Polish name for a rat is "szczur", which happens to match the above mentioned root. For the context, the prefix "pra-" has the same meaning as "grand" in "grand dad";
And so a Polish speaker who doesn't know of the antiquated meaning the word "praszczur" would hear it like "grand rat".
- The Russian (and generally Slavic) word for a bear is "медведь", which is colloquially has been disassembled into "мёд" (honey) and "ведь" ("to know" in this context, from "ведать" - "to be aware of"). So "honey-knower".
However, if you take a step back, you'll find out that initially the word was formed as "honey-eater" - not from *medъ and *věděti, but from *jěsti instead.
This etymology is further clouded in Polish, where there happened a shift from 'm' into 'n' in this word - "niedźwiedź". Honey remains with an 'm': "miód".
As an aside, in modern Russian the word would be constructed as "медоед" [medoed] - which is how the honey badger is currently called.