penknife n : a small pocketknife; originally used to cut quill pens [also: penknives (pl)]
A penknife or pen knife is a small folding pocket knife, originally used for cutting a quill to make a pen nib. It may have single or multiple blades and additional tools incorporated into the design.
Over the last hundred years there has been a proliferation of multi-function knives with multifarious and often ingenious gadgets including awls, reamers, scissors, nail files, corkscrews, tweezers, toothpicks and so on, and the tradition continues with the incorporation of modern devices such as ballpoint pens, LED flashlights and USB flash drives.
The most famous example of a multi-function knife is the Swiss Army knife, some versions of which number dozens of functions and are really more of a folding multi-tool, incorporating a blade or two, than a penknife with extras.
A larger folding knife, especially one where the blade locks into place, is often called a claspknife.
penknife in German: Federmesser
penknife in Swedish: Pennkniv