umbilicus — ONAD

umbilicus /ˌəmˈbilikəs, ˌəmˈbɪlɪkəs

▸ noun

(plural umbilici /-ˌkī, ˌ-ˌsī, -ˌkē/ or umbilicuses)

Anatomy the navel.

▪ Zoology a depression or hole at the center of the shell whorls of some gastropod mollusks and many ammonites.

▪ Zoology a hole at each end of the hollow shaft of a feather.

– ORIGIN late 17th century : from Latin: related to Greek omphalos, also to navel.