"full of zeal" (in the service of a person or cause), 1520s, from Medieval Latin zelosus "full of zeal" (source of Italian zeloso, Spanish celoso), from zelus (see zeal). The sense "fervent, inspired" was earlier in English in jealous (late 14c.), which is the same word but come up through French. Related: Zealously, zealousness.

c. 1600, from Italian zebra, perhaps via Portuguese, earlier applied to a now-extinct wild ass, of uncertain origin, said to be Congolese [OED], or Amharic [Klein], but perhaps ultimately from Latin equiferus "wild horse," from equus "horse" (see equine) + ferus (see fierce). Related: Zebrine; zebroid.

Asiatic ox, 1774, from French zebu, ultimately of Tibetan origin. First shown in Europe at the Paris fair of 1752.

masc. proper name, Biblical son of Jacob by Leah, from Hebrew Zebhulun, from zebhul "a dwelling" + diminutive suffix -on (see Genesis xxx.20).

masc. proper name, Biblical 11th of the Twelve Prophets; see Zachariah.

"the name of the letter Z in the alphabet," c. 1400, probably from Old French zede, from Late Latin zeta, from Greek zēta, from Hebrew zayin, letter name, literally "weapon;" so called in reference to the shape of this letter in ancient Hebrew. U.S. pronunciation zee is first attested 1670s. Other dialectal names for the letter are izzard, ezod, uzzard, and zod.

"the letter Z," 1670s, now more common in American English.

simple protein obtained from maize and wheat, 1822, from zea, Late Latin name for "spelt," from Greek zeia "one-seeded wheat, barley, corn" (from PIE root *yewo-) + -in (2).

in reference to spy-glasses or binoculars, 1905, from the firm founded by German optical instrument manufacturer Carl Zeiss (1816-1888).

1848, from German Zeitgeist (Herder, 1769), "spirit of the age," literally "time-spirit," from Zeit "time" (from Proto-Germanic *tidiz "division of time," from PIE root *da- "to divide") + Geist "spirit" (see ghost (n.)). Carlyle has it as a German word in "Sartor Resartus" (1831) and translates it as "Time-Spirit."