When was the White Feather first used as a symbol of cowardice?

Question

During WWI in Britain (and in some British colonies), a white feather was commonly given to men who were seen as cowards for not enlisting. The idea of using a white feather comes

supposedly from the sport of cock fighting, with the belief that cockerel’s [sic] sporting these white feathers were poor fighters

This propaganda campaign and method of shaming began in 1914 when the Order of the White Feather was started by Admiral Charles Fitzgerald and used women to shame men into enlisting as, at the time, there was no conscription. In what became a controversial campaign, women gave men who they thought hadn’t enlisted a white feather as a mark of shame or cowardice for failing to perform their duty. One problem was that some recipients were in reserved occupations while, in one case, a man received such a feather on the same day as the Victoria Cross.

The inspiration for this campaign seems to have come from the novel The Four Feathers published in 1902 and set in the late 19th century but, according to both Wikipedia and this article The Order of the White Feather, the tradition dates back to the 18th century. However, neither source gives any further details.

Are there any recorded incidences of white feathers being used in this way in the 18th century?

EDITED QUESTION

If not, when is the first recorded incidence of someone being given a white feather?

Answer 1

I've found several articles state that the OED dates the first usage of the term "white feather" as a symbol for cowardice to 1795. A representative example is White Feathers : Stories of Courage, Recruitment and Gender at the start of the Great War.

However, The Online Etymology Dictionary says the following:

white feather (n.) as a symbol of cowardice, 1785, said to be from the time when cock-fighting was respectable, and when the strain of game-cock in vogue had no white feathers, so that "having a white feather, is proof he is not of the true game breed" [Grose].

As far as I can make out, this appears to be a reference to A Classical Dictionary of the Vulgar Tongue by Francis Grose.

I couldn't locate a 1785 edition online, but the reference is certainly in the 1788 edition:

So it seems the OED may be mistaken!

Answer 2

See The Eustace Diamonds 1872 Trollope - Lord Fawn doesn't deserve the white feather for social cowardice ref: chapters 16-18