So, I have a question about the reconstruction of PIE consonants.
According to the Etymological Dictionaries, the words "rape" and "raven" have the same PIE root *ker- however how did "k" change into "r"? How did that come to be? I'd love to know if somebody could explain. Thank you in advance.
The idea is that the zero-grade of IE *ker, *kor, *kr gives Germanic hraben, with subsequent loss of the initial h-.
To add on to fdb's answer:
The change of initial PIE *k (and *ḱ) to Proto-Germanic *h is well-known (part of Grimm's Law), so that part of the derivation is completely expected and regular.
"Rape" might instead descend from Latin rapiō, in which case a different PIE root *h₁rep- "take away, snatch" has been proposed (compare Greek ἐρέπτομαι); Latin didn't have the same change of initial *k to *h (compare corvus > corvid).
