umbilicus (n.)

"navel," 1610s, from Latin umbilicus "the navel," also "the center" of anything, from PIE *ombh-alo-, suffixed variant form of root *(o)nobh- "navel" (see navel). In English, mostly confined to medical writing. Latin umbilicus is source of Spanish ombligo as well as Old French lombril, literally "the navel," from l'ombril, which by dissimilation became Modern French nombril (12c.).