Derivation Of The Term "Proof"

Well, according to the dictionary the word proof is defined as "the act of testing or making trial of anything; test; trial" So I would assume that the term proof in regards to coins refers to test or trial pieces.

In the United States at least to my knowledge in the 1800's proof patterns were given to congress men as presentation pieces before a new coin design was approved. Thus test or trial pieces.

Before about 1960, proof coins generally were made for the purpose as defined by casualcoincollector.
They were made with new dies, and the coins were often struck multiple times at increased strike pressure, to bring up all of the design detail. They looked like particularly well made business strikes. Such coins were kept by the mint, and were never intended for sale.
The Mint kept them as a standard for quality control purposes. They did not have mirror fields, and cameo details.

They were not intended for the collector. Because of the tiny number produced, they command huge prices at public auction.

Modern "proof" coins are made differently, with mirror fields and cameoed details, to satisfy the preferences of the modern "proof" coin collector. They are not made for test purposes. With some modern "proof" issues, huge numbers are produced, to the extent that the collector market will bear, so that profits for the Mint can be maximized.

The nearest modern mint product to the old genuine proof coins is 'Mint' or 'uncirculated' quality.

You might want to edit your post to say "to describe a coin that has highly reflective surfaces", as proof coins are not polished.

The term proof was used in several other fields for it was adopted by coin collectors. It was used in the printing field long long ago. Probably not too long after movable type was invented. The first sheet off a new rack of type referred to as a proof or a galley proof and used for examining search for errors in the type settings.

proof reading....testing to see if correct

proof copy....a printing of a book, for example, to check over before giving the publisher the go ahead to print the book.

proof is in the pudding...when the Congressman receiving a sample coin drops it in his dessert.

In the publishing business, the initial impressions of a typeset article are called proofs. You get these from the editor to make your markups on and correct errors before the article goes to press.

No? Maybe not always, but I have plenty of "classic" proofs with mirror fields and some even have cameo details.

Why, yes -- I'd love to share some pictures!