What is "start from scratch"

Scratch \Scratch\, n.

1. A break in the surface of a thing made by scratching, or by rubbing with anything pointed or rough; a slight wound, mark, furrow, or incision.

   The coarse file . . . makes deep scratches in the work.
   --Moxon.

   These nails with scratches deform my breast.
   --Prior.

   God forbid a shallow scratch should drive The prince of Wales from such a field as this.
   --Shak.

2. (Pugilistic Matches) A line across the prize ring; up to which boxers are brought when they join fight; hence, test, trial, or proof of courage; as, to bring to the scratch; to come up to the scratch. [Cant]
   --Grose.

3. pl. (Far.) Minute, but tender and troublesome, excoriations, covered with scabs, upon the heels of horses which have been used where it is very wet or muddy.
   --Law (Farmer's Veter. Adviser).

4. A kind of wig covering only a portion of the head.

5. (Billiards)

   1. A shot which scores by chance and not as intended by the player; a fluke. [Cant, U. S.]

   2. a shot which results in a penalty, such as dropping the cue ball in a pocket without hitting another ball.

6. In various sports, the line from which the start is made, except in the case of contestants receiving a distance handicap.

   Scratch cradle. See Cratch cradle, under Cratch.

   Scratch grass (Bot.), a climbing knotweed ( Polygonum sagittatum) with a square stem beset with fine recurved prickles along the angles.

   Scratch wig. Same as Scratch, 4, above.
   --Thackeray.

   start from scratch to start (again) from the very beginning; also, to start without resources.