the coiled, chambered fossil shell of an ammonoid.
Origin: 1700–10; < NL Ammonites < ML (cornū) Ammōn(is) (lit., horn of Ammon) + -ītes-ite1; fossil so called from its resemblance to the horn of Jupiter Ammon
"cephalopod mollusk," 1706, coined by Bruguière from M.L. (cornu) Ammonis "horn of Ammon," the Egyptian god of life and reproduction, who was depicted with ram's horns, which the fossils resemble.