The Proto-Indo-European sound k- changed into the h- sound into German (then English) — but it remained the k- sound (often spelled with c-) into Latin then Spanish. Thus we get many great parallels we’ve discussed before, such as head/cabeza. Another example of the same pattern:
Now look closely: if we remember that the h- in the Germanic/English words maps to the c- in Latinate/Spanish words, then it becomes very clear that the h-m-p of hemp maps the c-n-b of cannabis. The m/n and p/b cross and change very easily between each other, so those sound changes are much more obvious.
Who would’ve thunk!