The word Eccentric derives from Greek word Έκκεντρος (Έkentros) that is a word used in geometry.
Eccentricity in geometry is the measure of how much a conic section deviates from being circular.
The Έkentros meaning is something that “escapes” from center ((Εκ – κέντρος, εκ του κέντρου).
Eccentric so means someone that deviates from the normal (center) – a strange person. But this use of the word probably was used first in French. The Greek word for eccentric is Εκκεντρικός (Ekentrikόs).