1911 Encyclopædia Britannica/Jealousy
JEALOUSY (adapted from Fr. jalousie, formed from jaloux, jealous, Low Lat. zelosus, Gr. ζῆλος, ardour, zeal, from the root seen in ζέειν, to boil, ferment; cf. “yeast”), originally a condition of zealous emulation, and hence, in the usual modern sense, of resentment at being (or believing that one is or may be) supplanted or preferred in the love or affection of another, or in the enjoyment of some good regarded as properly one’s own. Jealousy is really a form of envy, but implies a feeling of personal claim which in envy or covetousness is wanting. The jealousy of God, as in Exod. xx. 5, “For I, the Lord thy God, am a jealous God,” has been defined by Pusey (Minor Prophets, 1860) as the attribute “whereby he does not endure the love of his creatures to be transferred from him.” “Jealous,” by etymology, is however, only another form of “zealous,” and the identity is exemplified by such expressions as “I have been very jealous for the Lord God of Hosts” (1 Kings xix. 10). A kind of glass, thick, ribbed and non-transparent, was formerly known as “jealous-glass,” and this application is seen in the borrowed French word jalousie, a blind or shutter, made of slats of wood, which slope in such a way as to admit air and a certain amount of light, while excluding rain and sun and inspection from without.