charcoalyoudaoicibaDictYouDict[charcoal 词源字典]
charcoal: [14] The words char and charcoal are related, but not in the way commonsense might lead one to suppose: for the verb char [17], originally apparently a charcoal-burner’s term, appears to derive from charcoal. So etymologically, the element char has nothing to do with ‘burning’. There are two main suggestions as to charcoal’s origins: firstly that it comes from Old French charbon ‘charcoal’ (related to English carbon); and secondly that it represents the now obsolete English verb chare (see CHARWOMAN), which in Old English times (cerran) meant ‘turn’.

On the basis of this theory, the etymological meaning of the word would be ‘turning into charcoal’ (for in Old English, coal meant ‘charcoal’ as well as ‘coal’).
[charcoal etymology, charcoal origin, 英语词源]
charcoal (n.)youdaoicibaDictYouDict
mid-14c., charcole, first element is either Old French charbon "charcoal," or, on the current theory, obsolete charren "to turn" (from Old English cerran) + cole "coal," thus, "to turn to coal."