From Greek 'zelos' (zeal, rivalry) via French — a doublet of 'zealous,' same root but opposite connotations.
Feeling resentment or suspicion because of a rival's advantages; fiercely protective or vigilant of one's rights or possessions.
From Old French jalous (jealous, zealous, envious), from Vulgar Latin *zelosus, from Late Latin zelus (zeal, fervour, jealousy), itself borrowed from Greek zêlos (zeal, ardour, jealousy, emulation). Greek zêlos derives from PIE *yeh₂- (to seek, to desire ardently). The same Greek root gives English zeal directly, and zealot (one consumed by zeal). The original senses
English 'jealous' and 'zealous' are doublets — two words from the same Greek source 'ζῆλος' (zēlos) that entered English by different routes. 'Zealous' came directly through Latin 'zēlōsus,' keeping the 'z.' 'Jealous' came through Old French, where the 'z' shifted to 'j' through regular sound change