A lot vs. Alot: 9 Grammatical Pitfalls
1830, from French cadre, literally "a frame of a picture" (16c.), so, "a detachment forming the skeleton of a regiment" (1851), from Italian quadro, from Latin quadrum "a square" (see quadrille). The communist sense is from 1930.
An elite or select group that forms the core of an organization and is capable of training new members.