When Hell freezes over

Your best bet would probably be the OED. That can date anything in the English language back to its origins.

A little googling found this, which doesn't have the info you seek:
http://idioms.thefreedictionary.com/until+hell+freezes+over
However, it gives this book as a reference, though the description/editorial review doesn't seem to indicate that it has what you want:
http://www.cambridge.org/elt/elt_projectpage.asp?id=2501153
This one however, says: "This dictionary features full-sentence examples showing how idioms are really used, usage and origin notes that expand on the definitions, and ample cross-references." (bolding by me)
http://www.amazon.com/dp/052153271X/?tag=absolutewritedm-20
Hope this helps...


ETA: the thread isn't complete without this link:
http://www.netjeff.com/humor/item.cgi?file=hell.thermo.txt

From the Online Etymology Dictionary:

hell
O.E. hel, helle "nether world, abode of the dead, infernal regions," from P.Gmc. *khaljo (cf. O.Fris. helle, O.N. hel, Ger. Hölle, Goth. halja "hell") "the underworld," lit. "concealed place," from PIE *kel- "to cover, conceal, save" (see cell). The Eng. word may be in part from O.N. Hel (from P.Gmc. *khalija "one who covers up or hides something"), in Norse mythology Loki's daughter, who rules over the evil dead in Niflheim, the lowest of all worlds (nifl "mist"), a death aspect of the three-fold goddess. Transfer of a pagan concept and word to a Christian idiom, used in the K.J.V. for O.T. Heb. Sheol, N.T. Gk. Hades, Gehenna. Used figuratively for "any bad experience" since at least 1374. As an expression of disgust, etc., first recorded 1678. Hell-bent is from 1835. Hell-raiser is from 1914 (to raise hell is from 1896); hellacious is 1930s college slang. Expression Hell in a handbasket is c.1941, perhaps a revision of earlier heaven in a handbasket (c.1913), with a sense of "easy passage" to whichever destination. Expression hell of a _____ is attested from 1776. Hell or high water is apparently a variation of between the devil and the deep blue sea. To wish someone would go to hell is in Shakespeare (1596). Snowball's chance in hell "no chance" is from 1931; till hell freezes over "never" is from 1919. To ride hell for leather is from 1889, originally with reference to riding on horseback. Hell on wheels is from 1843.

I found the same date - 1919 - listed in a few other dictionarys online and off but I can't vouch for the accuracy. I would feel better if the original source in 1919 was cited but maybe this well help! I used to have a book that gave the historys of a lot of idioms called "A Hog on Ice" - if you could find it, you might look there!

The OED also gives 1919:

h. when, till, until hell freezes (over): advb. phr. indicating a date in the impossibly distant future, for ever. 1919 J. A. FISHER Let. 13 June in Henry Bristow Ltd. Catal. (1973) No. 203.9 Yours till hell freezes. 1931 Amer. Speech VI. 435 Till hell freezes over. 1949 Romance Philol. II. 105 We have the meaning ‘forever’ in ‘I'll wait until Hell freezes over’ and the meaning ‘never’ in ‘I'll do it when Hell freezes over’. 1961 ‘A. A. FAIR’ Stop at Red Light (1962) ii. 36 If their suspicions once get aroused, they'll investigate until hell freezes over. 1962 Listener 1 Nov. 704/1 ‘I am prepared,’ Mr Stevenson rasped out, ‘to wait for an answer till hell freezes over.’ 1966 Guardian 17 Aug. 9/2 The Texan chairman..declared that he would..open the hearing today even if it meant going to gaol ‘until hell freezes’.

Click to expand...

For what it's worth, I've found a reference that might put the usage back a few years. In his autobiography Trials of a Lawyer, James Manahan quotes A.C. Townley at the time of the creation of the Non-partisan League (a farmers' organization in North Dakota) as saying "Make the rubes pay their god-damn money to join and they'll stick--they'll stick till hell freezes over." The league was founded in 1915, but I guess there's no proof Manahan remembered it correctly (I'm also not sure when he wrote the book--the only pub date I've seen for it is 1933, a year after he died).

There's also a reference in a June 1920 academic journal (“De Profanitate” Tenney L. Davis, The Journal of Philosophy, Psychology, and Scientific Method Vol. 17 No. 12):

The youthful enthusiast swears loyalty to his purpose “till Hell freezes over”

That would be a quick spread to general usage if the phrase only originated in 1919. Not impossible, but quick.

And a 1929 article says it's an old Maine saying, but with no date attached:

Of an opinionated man it was said "you can't make a dent in him," of a determined one "he would wait until Hell freezes over and meet you on the other side"
("More Notes on Maine Dialect" by Anne E. Perkins, American Speech Vol. 5 No. 2, Dec. 1929)

ETA: Here's a similar phrase from 1867: I'll stay wif yu till thar's enuf fros' in hell tu kill snap-beans.' (George Washington Harris, Sut Lovingood. Yarns Spun by a "Nat'ral Born Durn'd Fool." Warped and Wove for Public Wear)

Looking at googlebooks, there's no hit for this phrase before latter C19.

It is memorably mentioned here

General Granger says "I am in possession of Knoxville and will hold it till Hell freezes over."

This may be an early mention. A popularlizing mention. And we see it used right after this.