Nutshell (noun)

1. The hard outer shell of a nut.
2. A short or concise summary of something, the essence of something.

Origin:

The word "nutshell" comes from the old english word "hnutu" meaning "nut" and "scealu" meaning "shell" which combine to mean "the shell of a nut".

Examples:

1. He cracked the nutshell to get to the nut inside.
2. The nutshell is the protective outer layer of the nut.
3. She gave a nutshell of her presentation before starting.
4. In a nutshell, the proposal is to build a new bridge.
5. He explained the whole situation in a nutshell.