fervor for a person, cause, or object; eager desire or endeavor; enthusiastic diligence; ardor.
Origin of zeal
1350–1400; Middle English zele < Late Latin zēlus < Greek zêlos
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
fervent or enthusiastic devotion, often extreme or fanatical in nature, as to a religious movement, political cause, ideal, or aspiration
Word Origin for zeal
C14: from Late Latin zēlus, from Greek zēlos
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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.
Online Etymology Dictionary, © 2010 Douglas Harper