What is the X in X-mas?
c.1200, nute-scalen; see nut + shell (n.). Figurative use with reference to "great condensation" (1570s) supposedly originally is a reference to a copy of the "Iliad," mentioned by Pliny, which was so small it could fit into the shell of a nut.
To condense; sum up: If I'm forced to nutshell it, the show is about community, it's about the workplace and the town
[1883+; fr the idiom put something in a nutshell]