noun
- fervor for a person, cause, or object; eager desire or endeavor; enthusiastic diligence; ardor.
noun
- fervent or enthusiastic devotion, often extreme or fanatical in nature, as to a religious movement, political cause, ideal, or aspiration
late 14c., from Late Latin zelus “zeal, emulation” (source of Old French zel, Italian zelo, Spanish celo), a Church word, from Greek zelos “zeal, ardor, jealousy,” which is of uncertain origin.