penknife

From Middle English penne knyfe; equivalent to pen + knife. In the original sense, named for its purpose: aiding the use of a (traditional) ink pen through the following tasks: trimming the tip of a quill pen, trimming a reed for a nib, and (in some cases) allowing erasure by scraping away some ink.

出典: Wiktionary「penknife」（CC BY-SA 4.0）