Zealous vs. Jealous

Zealous and jealous share not just a rhyme, but an etymology. Both words ultimately come from the Latin zelus “jealousy,” and in the past their meanings were somewhat closer to each other than they are today. In the 16th and 17th centuries, zealous occasionally was used in biblical writing to refer to a quality of apprehensiveness or jealousy of another. By the 18th century, however, it had completely diverged in meaning from jealous, signifying “warmly engaged or ardent on behalf of someone or something.” Today, zealous often carries a connotation of excessive feeling: it typically means “fiercely partisan” or “uncompromisingly enthusiastic.”