The traditional form 筆 combines 竹, “bamboo”, with 聿, an old graph associated with a hand holding a writing brush. Bamboo was a natural material for brush shafts. Simplified 笔 keeps the bamboo top and reduces the lower part. The early history of the full compound is later than the oldest oracle-bone writing, so this ancient-form-inspired sketch shows the components rather than claiming to copy an oracle-bone form.
A piece of culture
One of the Four Treasures The writing brush is one of the traditional Four Treasures of the Study, together with ink, paper and inkstone. Calligraphers vary pressure, speed and angle so a single brush can make both fine lines and broad, energetic strokes. Today 笔 / 筆 also appears in everyday words for modern pens and pencils.