nutshell (n.)

c. 1200, nute-scale, "hard shell which forms the covering of the kernel of a nut;" see nut (n.) + shell (n.). Figurative use with reference to "great condensation" (1570s, as in in a nutshell) supposedly originally is a reference to a tiny copy of the "Iliad," mentioned by Pliny (and in English from late 14c.), which could fit into the shell of a nut.