why is a pen knife called a pen knife
A penknife, or pen knife, is a British English term for a small folding knife. One popular folk etymology makes an association between the size of a penknife and a small ballpoint pen, however the phrase "penknife" is much older. Originally, penknives were used for thinning and pointing quills to prepare them for use as dip pens and, later, for repairing or re-pointing the nib. They did not necessarily have folding blades, but resembled a scalpel or wood knife by having a short, fixed blade at the end of a long handle.