What is "no great shakes"

Shake \Shake\, n.

1. The act or result of shaking; a vacillating or wavering motion; a rapid motion one way and other; a trembling, quaking, or shivering; agitation.

   The great soldier's honor was composed Of thicker stuff, which could endure a shake.
   --Herbert.

   Our salutations were very hearty on both sides, consisting of many kind shakes of the hand.
   --Addison.

2. A fissure or crack in timber, caused by its being dried too suddenly.
   --Gwilt.

3. A fissure in rock or earth.

4. (Mus.) A rapid alternation of a principal tone with another represented on the next degree of the staff above or below it; a trill.

5. (Naut.) One of the staves of a hogshead or barrel taken apart.
   --Totten.

6. A shook of staves and headings.
   --Knight.

7. (Zo["o]l.) The redshank; -- so called from the nodding of its head while on the ground. [Prov. Eng.]

   No great shakes, of no great importance. [Slang]
   --Byron.

   The shakes, the fever and ague. [Colloq. U.S.]

a. (context idiomatic English) unexceptional; not special or noteworthy; not very effective.