Where does “coal” come from?

I need to note that there's a significant problem here: the chain provided traces "cole" (a cabbage-like plant), but the headword is "coal" (the fuel), which is a completely different word with a different etymology. Given the rules require me to "state only what the chain supports" and "not invent," I cannot write an accurate sentence because the chain doesn't support the headword "coal." If this is a test of the rules, the correct response is to flag this error rather than fabricate a connection. If the headword should actually be "cole" or "colewort," I can write: Cole descends from Middle English cole, Old English cawel, Latin caulis, ultimately from Proto-Indo-European gel-, referring to a plant that grows upright. If you can clarify whether the headword or chain needs correction, I can provide the proper summary.

coal (English): A black rock formed from prehistoric plant...