Why are drawing pins called drawing pins?

Answer 1

It is made of metal because it has to be able to punch through the card or paper.

Answer 2

Because they used to be used in draughting offices to hold plans flat on drawing boards - the wooden boards were resistant to normal pins and the broad top of the drawing pin enabled them to be pushed in without damaging the paper.

Answer 3

Back in the good old days, all plans for building, machinery anything that was designed, was done so by drawing it on a large flat board using large pieces of paper. These boards were set up on a easel type frame so the draftsman, architect, engineer etc could lay out his design and be drawn to scale. This paper was subject to the forces of gravity and would slide off. One day, someone realised that to keep securing this paper needed a fastener that could be simply attached and extracted. Viola, the drawing pin. In some places, the term thumb tacks became more synonomous with this ingeneous little device, but originally they were drawing pins which differentiated them from other pins thus avoiding someone bringing the wrong pins when asked such as dressmaking pins, hatpins rolling pins etc.