Listening to an interview (BBC, so British English), I heard an author describe an actress's performance "as near as dammit" to the novel's character. I was confused enough to listen again, and had heard it correctly.
From the context, the meaning was clear: very nearly exactly. Looking it up, all the dictionaries gave the same meaning, but no explanation. The Online Etymology Dictionary gave the usual definition of damn:
late 13c., "to condemn," from Old French damner "damn, condemn; convict, blame; injure," derivative of Latin damnare "to adjudge guilty; to doom; to condemn, blame, reject," from noun damnum "damage, hurt, harm; loss, injury; a fine, penalty," from Proto-Italic *dapno-, possibly from an ancient religious term from PIE *dap- "to apportion in exchange" [see Watkins]. The Latin word evolved a legal meaning of "pronounce judgment upon." Theological sense is first recorded early 14c.; the optative expletive use likely is as old.
I'm very interested in how "dammit" came to mean, in effect, exact, or lacking that, how the phrase came to mean "as close to exactly".
I'm limited to a phone and don't know how to link, sorry. I'm a dinosaur.
Best Answer
Vijay Kumar, Sterling Dictionary of Idioms (1998) reports that "as near as dammit" and "as near as makes no difference" are variant expressions of the same idea:
Two other very similar expressions are "as near as makes no odds" and "as near as makes no matter," both of which appear in Norman Schur, British English from A to Zed: A Definitive Guide to the Queen's English, second edition (2013)—which JOSH quotes in his answer. Here is that reference work's treatment of the relevant expressions:
G.F. Northall, "Folk-phrases of Four Counties (Glouc., Staff., Warw. Worc.)" (1894) lists "As near as damn it" without any specific county attribution, meaning that it was then current in all four.
The "as near as makes no difference/odds/matter" wordings are perhaps clearer on their face than "as near as dammit/damn it", but all appear to be of roughly similar age, to judge from Google Books search results. As JOSH notes in his answer the earliest Google Books match for "as near ... as dammit" is from 1871.
But the earliest Google Books matches for the other versions are very nearly as old. From a letter (dated June 18, 1877) by H. Hunt to the editor of The Fishing Gazette (June 22, 1877):
From J.P.W., "Trout Fishing at Mill-Head" (July 19, 1878):
And (somewhat later) from Platelayer, Great Northern Railway, "A Night in the Fog," in Railway Herald Magazine (January 1895):
An Elephind search turns up instances of this last phrase from as early as 1886. From a letter to the editor of the [Perth, Western Australia] Daily News (May 1, 1886):
I can't tell whether the "as makes no difference/odds/matter" family represent a euphemistic toning-down of the "as dammit/damn it" duo, or whether the latter represent cacophemisms of the former. But all seem to have appeared in historically close proximity to one another, in Britain or its possessions, and with extremely similar meanings.