umbilical: [16] Umbilical was borrowed from medieval Latin umbilīcālis, a derivative of Latin umbilīcus ‘navel’. This went back ultimately to the Indo-European base *onobh-, a variant of which, *nobh-, produced English navel [OE]. => navel[umbilical etymology, umbilical origin, 英语词源]
"pertaining to the navel," 1540s, from Medieval Latin umbilicalis "of the navel," from Latin umbilicus "navel" (see umbilicus). Umbilical cord attested by 1753 (the native term is navel string).