Old English nafela, nabula, from Proto-Germanic *nabalan (source also of Old Norse nafli, Danish and Swedish navle, Old Frisian navla, Middle Dutch and Dutch navel, Old High German nabalo, German Nabel), from PIE *(o)nobh- "navel" (source also of Sanskrit nabhila "navel, nave, relationship;" Avestan nafa "navel," naba-nazdishta "next of kin;" Persian naf; Latin umbilicus "navel;" Old Prussian nabis "navel;" Greek omphalos; Old Irish imbliu). For Romanic words, see umbilicus.
The cords of all link back, strandentwining cable of all flesh. [Joyce, "Ulysses"]
"Navel" words from other roots include Lithuanian bamba, Sanskrit bimba- (also "disk, sphere"), Greek bembix, literally "whirlpool." Old Church Slavonic papuku, Lithuanian pumpuras are originally "bud." Considered a feminine sexual center since ancient times, and still in parts of the Middle East, India, and Japan. In medieval Europe, it was averred that "[t]he seat of wantonness in women is the navel." [Cambridge bestiary, C.U.L. ii.4.26] Words for it in most languages have a secondary sense of "center." Meaning "center or hub of a country" is attested in English from late 14c. To contemplate (one's) navel "meditate" is from 1933; hence navel-gazer (1952); see also omphaloskepsis. Navel orange attested from 1888.