On the origin and usage of 'sight unseen'

Question

The expression sight unseen means:

• Without having viewed the object in question, as in He bought the horse sight unseen.

The American Heritage Dictionary notes that:

• This seeming oxymoron (how can a sight, which means something seen, be not seen?) dates from the late 1800s.

According to Grammarphobia:

• The Oxford English Dictionary says “sight unseen” is an American expression for “without inspection” and dates from the 1890s. The OED’s earliest citation, from 1892, is in Dialect Notes, a journal of the American Dialect Society: “To trade knives sight unseen is to swap without seeing each other’s knife.”

There appear to be earlier usages of the expression as in A History of American Mannfactores from 1608 to 1860, published in 1866 :

• The price of a cow and calf, he says, was 50s., " sight unseen, be she big or little, they are never very curious to examine that point."

My questions:

1. What is the origin and first usage of this idiomatic expression?

2. What are other common idiomatic expressions (AmE or BrE) that convey the same meaning?

Answer 1

Here is documentation that your 1866 example in your post is actually from 1694 or earlier, in a description "of the Beasts of Virginia," by Mr. John Clayton.

From Google books, Philsophical Transactions, vol XVIII, London.

The Common Rate of a Cow and Calf, is 50 s. sight unseen, be she big or little, they are never very Curious to Examine that Point.

There is a very similar expression that means the same thing, and which seems much more common in the 18th century: unsight, unseen. The earliest I can find this expression in Google books is from 1694, in Hudibras by Samuel Butler:

For to subscribe, unsight, unseen,
T' an unknown Church Discipline,
What is it else, but beforehand,
T' ingage, and after understand?

The OED dates unsight, unseen (Obs.) to 1627:

a1627 T. Middleton & W. Rowley Old Law (1656), Take that at hazard sir... Unsight, unseen, I take 3. to one.
1632 R. Brome Northern Lasse, I would I had his Neece unsight and unseen I faith for her monies sake.

So I would conjecture that sight unseen originated from an alteration of unsight unseen. This alteration makes some sense, and replaces the word unsight, which the OED says is used as an adjective only in that expression. The OED's guess at the etymology of unsight, unseen is that it is a corrupted or dialect version of unsighted, unseen. But they attach a question mark to this etymology, so they aren't very sure about this.

Answer 2

"Sight Unseen" originated from when guns were used on a daily basis, when a gun was shot without looking at the gun's sight. i.e. Shooting from the hip or in a fashion where the sights are not used. Example: The cowboy hit the target sight unseen.