What is the origin of skinflint and the image it is derived from

Skinflint is an old expression, probably from thieves slang, whose meaning suggested the idea that one would even skin a flint to save something of it.

The noun skinflint, which denotes a niggardly person, is first recorded in A New Dictionary of the Terms Ancient and Modern of the Canting Crew (London, 1699), by “B. E. Gent.”:

• Skin-flint, a griping, sharping, close-fisted Fellow.

It is from the hyperbolical phrase to skin a flint, denoting excessive meanness or the willingness to go to extreme lengths to save or gain something.

This is comparable to the French phrase tondre un œuf (to shave an egg), which used to be tondre sur un œuf (to shave on an egg); Randle Cotgrave defined it in A Dictionarie of the French and English Tongues (1611):

Tondre sur vn oeuf. To accuse truth of falsehood, charge vertue with vice, find a fault where there is none; also, to make a commoditie of any thing, how bare soeuer it be; whence, Ils trouveront à tondre sur vn oeuf (= They will find [something] to shave on an egg).

The phrase to skin a flint is first recorded in one of the poems introducing the 1656 edition (London) of The Legend of Captain Jones. Relating His adventure to Sea: His first landing, and strange Combat with a mighty Bear.

This were but petty hardship, Jones was one

Would Skinne a Flint, and eat him when h’had done.

(Wordhistories.com)

Lexicographer Craig M. Carver suggests that the idea skinning a flint may derive from riflemen:

The flint in skinflint is the hard stone used to spark fires when struck with iron or steel. Craig M. Carver, lexicographer and managing editor of the Dictionary of American Regional English writes about flint and its role in riflery, and how this inspired the word “skinflint”:

• [The rifle] used a piece of flint held in a hammerlike device, or “cock.” When the trigger was pulled, the spring-loaded cock struck the flint against a steel plate… creating a shower of sparks. The flash of the priming powder in the pan just beneath the steel plate ignited the charge in the bore and fired the weapon... After repeated firings, the flint wore down. Most riflemen merely replaced the flint, but some penny-pinchers “skinned” or sharpened their flints with a knife.

(www.bozemandailychronicle.com)