"Camel hair" is, among other things, the hair of a camel.
Since we talk about "sheep's wool" or "lamb's wool", why don't we use the "'s" after camel in the case above?
Perhaps some historical reason might exist, but, as a not native of English language I'm wondering if I have to learn all the cases in reference to any specific animal or if there exists some guidance, if not some rule, helping to understand this problem.
For example, if the separation of an animal's part implies its death, can I be sure that the "'s" has to be dropped, as in the case of "calf skin"?
If this is a real rule, could we extend it to human beings? For example, if one—a doctor, for example—talks about my heart, after my death, should s/he say "Carlo's heart" or "Carlo heart"?