"the mark in the middle of the belly where the umbilical cord was attached in the fetus," Middle English navele, from 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 (by 1947); see also omphaloskepsis. Navel orange is attested from 1831.
Another great key I will give you is to be found by the contemplation of the Manipur Lotus, which is in the navel, or thereabouts. By contemplating this center you will be able to enter and go into another person's body, and to take possession of that person's mind, and to cause him to think and to do what you want him to do; you will obtain the power of transmuting metals, of healing the sick and afflicted, and of seership. ["Swami Brahmavidya," "Transcendent-Science or The Science of Self Knowledge," Chicago, 1922]