As a noun, a pencil is a writing tool with a thin stick of graphite or similar material inside a wood or plastic case. As a verb, “to pencil in” means to schedule something in a way that can still be changed.
“Pencil” comes from Old French *pincel*, meaning “small paintbrush,” from Latin *pencillus*, “little tail,” referring to the brush’s bristles. It originally described a fine brush before shifting to the modern writing tool.
Before it meant graphite in wood, “pencil” meant a tiny paintbrush with a tail of hair. So “penciling” something in is like sketching it lightly with an artist’s tool—easy to change. The word keeps a faint memory of art inside everyday writing.
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