core (n.) Look up core at Dictionary.com
late 14c., probably from Old French coeur "core of fruit, heart of lettuce," literally "heart," from Latin cor "heart," from PIE root *kerd- "heart" (see heart). Nuclear reactor sense is from 1949.
core (v.) Look up core at Dictionary.com
mid-15c., from core (n.). Related: Cored; coring.