Charcoal

google

ref

late Middle English: probably related to coal in the early sense ‘charcoal’.

wiktionary

ref

From Middle English charcole, from charren(“to change, turn”) + cole(“coal”), from Old English cierran(“to change, turn”) + col(“coal”); equivalent to char(Etymology 3 (verb)) +‎ coal.

etymonline

ref

charcoal (n.)

"coal made by subjecting wood to smothered combustion," 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."