means A flat, usually semicircular instrument marked in degrees, used to measure and draw angles.

from From Latin protractus, the past participle of protrahere, "to draw forth or drag out" — pro- "forward" plus trahere "to pull" (the same root that gives us tractor and traction). It first meant simply one who or that which draws out, and by the 17th century the geometer's angle-measuring tool had pulled the name to itself.