Greek 'ek-' (out of) + 'kentron' (center) — originally an off-center orbit, applied to people by the 1620s.
Unconventional and slightly strange in behavior or appearance; deviating from an established pattern.
From Medieval Latin "eccentricus" (not having the earth as its centre), from Greek "ἔκκεντρος" (ékkentros, out of the centre), a compound of "ἐκ" (ek, out of, from PIE *h₁eǵʰs, out of) + "κέντρον" (kéntron, centre, sharp point, goad, from PIE *ḱent-, to prick, to sting). The word was first an astronomical term: in Ptolemaic astronomy, an "eccentric" orbit was one whose centre did not coincide with the Earth — a crucial concept for explaining planetary motion before Copernicus. The "κέντρον" originally meant a sharp point or goad for driving cattle, then the
Greek 'kentron' (center) originally meant 'a sharp point' — specifically the stationary point of a compass around which the circle is drawn. The same root gives us 'center' and, through Latin 'centrum,' 'concentrate,' 'concentric,' and 'centrifugal.' An eccentric person is one whose orbit