c.1300 (implied in smoldering), "to smother, suffocate," cognate with Middle Dutch smolen, Low German smelen, Flemish smoel "hot," from Proto-Germanic *smel-, *smul-. The meaning "burn and smoke without flame" is first recorded 1520s, fell from use 17c. (though smoldering persisted in poetry) and was revived 19c. Related: Smouldered.