If you're asking why we use those words in English to refer to Russia and Germany, that's more of an etymological question, but the simple answer is that they refer to themselves that way.

The Russian word "родина" (pronounced "rodina") means "homeland", especially referring to Russia, and it comes from a very common root word in reconstructed Proto-Slavic: "*rodъ". (The asterisk shows that we don't have any concrete evidence that the word was spelled that way, so we've reconstructed it by comparing cognates in various Slavic languages, and the weird thing at the end that looks like a b is an "uh" sound in Proto-Slavic that is not pronounced in modern Russian.) This root has produced the words for "birth", "parents", "to be born", "harvest", and many others in modern Russian, so it clearly had something to do with generation and caretaking. The word is also often paired with the literal word for mother ("родина-мать"), cementing the connection in many Russians' minds.

I feel I should add here that, though "rodina" is certainly the most common way of referring to the idea of a homeland in Russian, the words "отечество" and "отчизна", both of which come from the same root as "отец", meaning "father", are also used.

As for German use, well, they sometimes refer to Germany as "das Vaterland". I don't need to explain that any further.

If you're asking why the Russians and Germans use those words in the first place, well, I don't think I need to cite any sources to prove that people think of their homeland as having raised and provided for them.

Source for the etymology: Etymological dictionary of the Russian language, by Max Vasmer, p. 589.

EDIT: Fixed some errors.

Related question; has anybody ever used "brotherland" or "sisterland?"