English

The expression refers to the tidy, compact package.

Adverb

in a nutshell

1. (idiomatic) In summary; briefly or simply.

   He had a lot to say, but his answer, in a nutshell, was no.

   • 1899, Joseph Conrad, Heart of Darkness, section 1

     The yarns of seamen have a direct simplicity, the whole meaning of which lies within the shell of a cracked nut.

Translations