Merriam-Webster's Collegiate® Dictionary, 11th Edition
CURB
I. noun
Etymology: Middle French courbe curve, curved piece of wood or iron, from courbe curved, from Latin curvus
Date: 15th century
a bit that exerts severe pressure on a horse's jaws, an enclosing frame, border, or edging, check , restraint , a raised edge or margin to strengthen or confine, an edging (as of concrete) built along a street to form part of a gutter, a market for trading in securities not listed on a stock exchange,
II. transitive verb
Date: 1530
to furnish with a curb, to check or control with or as if with a curb , to lead (a dog) to a suitable place (as a gutter) for defecation, see: restrain