What is the story behind the phrase 'as it were'? Where did it come from?

Solution 1:

The form were is a past subjunctive, and it is used in a construction that is common in hypothetical situations:

He would kill me if he were able.

She behaves as [would be fitting / etc.] if she were upper class.

The phrase is theoretically short for as [it would be if] it were [so], though it is uncertain whether that is really where it came from.

The Oxford English Dictionary (2nd ed.) has its earliest quote from circa 1386:

As it were: as if it were so, if one might so put it, in some sort: a parenthetic phrase used to indicate that a word or statement is perhaps not formally exact though practically right.

• c1386 Chaucer Nun's Pr. T. 26 She was as it were a maner deye.

• 1399 Langl. P. Pl. C. ix. 22 Ich wolde a-saye som tyme for solas, as hit were.

• 1531 Elyot Gov. (1834) 211 It draweth a man as it were by violence.

• 1579 E. K. in Spenser's Sheph. Cal. Mar. 11 Gloss., The messenger, and as it were, the forerunner of springe.

• 1692 E. Walker Epictetus' Mor. (1737) xxii, You're as it were the Actor of a Play.

• 1711 Steele Spect. No. 32 31 She has thought fit, as it were, to mock herself.

• 1881 Buchanan God & Man I. 124 She took him at once, as it were, into her confidence.

Solution 2:

Webster's 3rd New Int'l Dictionary gives its meaning as:

as it were: as if it were so : in a manner of speaking <her triumph, as it were, did not last long>

The Oxford English Dictionary dates its first written usage by Chaucer c. 1386.

Solution 3:

According to the Oxford English Dictionary, it's quite an ancient phrase that emerged from an archaic form of the subjunctive mood:

a. Introducing a supposition, expressed by the subjunctive mood: As if, as though. arch.

1135 Anglo-Saxon Chron., Uuard þe sunne suilc als it uuare thre niht ald mone.

As the definition above suggests, a rough modern English equivalent to this original use might be 'as if,' as in 'he reeled as if hit by a sledgehammer.'

The OED dates its current sense to c1400:

c1400 (1387) Langland Piers Plowman (Huntington HM 137) C. ix. l. 22 Ich wolde a-saye som tyme for solas, as hit were.

c1405 (1390) Chaucer Nun's Priest's Tale (Hengwrt) (2003) l. 26 She was as it were a maner deye.

1531 T. Elyot Bk. named Gouernour iii. xi. sig. ci, It draweth a man as it were by violence.

These uses are clearly different from the original, and closer to the modern use, but it's not hard to imagine a plausible narrative to explain how they might have arisen from the original.