Derringer and Six-gun

Derringer noun - A pocket pistol of large caliber with a short barrel.

Six-gun and derringer are semantically related. In some cases you can use "Six-gun" instead a noun "Derringer".

Six-gun noun - A pistol with a revolving cylinder (usually having six chambers for bullets).

Derringer and six-gun are semantically related. You can use "Derringer" instead a noun phrase "Six-gun".