also omphalus, "sacred stone," 1850, from Greek omphalos, literally "navel," later also "hub" (as the central point), from PIE *ombh-alo-, from root *nobh-/*ombh- "navel" (see navel). Especially as the name of the rounded or conical stone in the shrine at Delphi, regarded by the ancients as the center of the world. Related: Omphalic.
1925, from omphalo- + Greek -skepsis, from skeptesthai "to reflect, look, view" (from PIE root *spek- "to observe"). Also omphaloscopy (1931). Used earlier in the sense of "navel-gazer" were omphalopsychic (1892) and Omphalopsychite (1882) "one of a body of monks who believed the deep contemplation of the navel induced communion with God," a derisive name given to the Hesychasts.
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Harper, D. (n.d.). Etymology of omphalo-. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/omphalo-