The phrase that job’s jobbed means it’s finished, it’s all over.

It is used to express satisfaction when a task that has called for more than usual enterprise and determination has been accomplished.

The verb job, first recorded in 1647, means to do a job. An interesting play on the noun job, the verb job and the noun jobber occurs in the following letter, published in The Evening Packet, and Correspondent (Dublin, County Dublin, Ireland) of Saturday 14^th February 1835:

On reading the account of the sailing of the expedition of the Euphrates, in your consistent journal of the 7^th instant, I was exceedingly grieved to reflect that so much valuable time, money, and perhaps lives, were about to be sacrificed, upon what, in my opinion, is almost an useless enterprise. In the early part of last Session a Committee of the House of Commons was appointed by the late Government to receive evidence as to the best method of effecting a steam communication with India. It might naturally have been supposed that this Committee would have directed some portion of their inquiries as to the possibility of navigating steam vessels by the way of the Cape of Good Hope—a road so well known to the English seaman, and where the foreigner can levy no tribute; but no, these gentlemen, under the management of Mr. Charles Grant, their Chairman, made their minds to direct their inquiries only to the possibility of effecting this object by the way of the Mediterranean and Persian Gulph, and upon the strength of this left-handed evidence they got a vote of 20,000l. of the public money—to do what?—why, to send out a party of naval and military men, to construct roads in an enemy’s country, of an extent of 250 miles, and then to survey and render navigable an extent of river of upwards of 800 miles, by blasting all the rocks and removing other impediments which may obstruct them in their progress down. Sure I am, that if ever this party of 50 men reach the banks of the Euphrates, with their iron steem-boats [sic] and diving-bells, they will have quite enough work in rock-rending for the next twenty years at least, if the published accounts of this river may be at all depended upon, to say nothing of the difficulties of land travelling, warfare, plague, &c., for which that part of the world is quite notorious. Now, I do not hesitate to say that this, on the part of the defunct Whig Government, is as complete a job as the Russian loan job, the Abercromby job, or any other of the many jobs, jobbed by these notorious jobbers—because it has been proved to a demonstration by practical seafaring, as well as scientific men, that the voyage to India can with certainty be accomplished within 70 days, by that truly English road, the broad blue sea, by steamers of sufficient dimensions, and properly equipped, and therefore there is certainly no necessity for spending 20,000l. of the public money in improving an enemy’s country, and diverting the channel of industry from that route which has been so long and so ably navigated by the British seaman.

A synonym of that job’s jobbed, the earlier phrase the job’s jobbed is first recorded in Exchange no Robbery (London: John Cumberland, 1825?), a comedy by the British author Theodore Edward Hook (1788-1841), first performed in 1820 at the Theatre Royal, Haymarket, London:

Mrs. S. Then why don’t you try a new plan? […] Put yourself under my guidance, and the job’s jobbed.

The earliest occurrence of that job’s jobbed that I have found is from The Invisible Gentleman (Volume III – London: Edward Bull, 1833), by James Dalton, a British author active in the 1830s:

“As Sir William says he knows a sure way of getting you out of the scrape—why that job’s jobbed, as we say.”

The phrase then occurs in the following from John Bull (London, England) of Sunday 3^rd March 1839:

What the real nature may be of the game that Ministers are playing we leave those of themselves—who are permitted to know—to decide; for as to the People generally, we defy them to comprehend the trickery and jobbery which are going on, or their end or object.
There never could have been, as we have said over and over again, a Lord Lieutenant better calculated to play the part than Lord Normanby ¹, and the only possible reasons—except some private considerations of his own—for removing his Excellency from his Vice-royalty were, that from a heedless love of popularity, and a wrong twist in politics, he had so completely thrown himself into the hands, and under the influence, of O’Connell ² and the Priests, that he had not only committed the Government more seriously than Lord Melbourne ³ (during the few moments in the day which he devotes to business) ever wished or intended, but that in consequence the respectable portion of Irish society had abandoned the Court, and that in fact the administration of affairs was confided to that class of persons whose hostility to the existing institutions was notorious, and with whom the overthrow of the Church and the Repeal of the Union had become a sine quâ non.
Just at this crisis Lord Melbourne thinks it right to get rid of Lord Glenelg ⁴; Lord Normanby comes over, and that “job is jobbed;” the Lord-Lieutenant goes back, and the notion of his removal is laughed at.

¹ Constantine Henry Phipps (1797-1863), 1^st Marquess of Normanby, served as Lord Lieutenant of Ireland from 28^th April 1835 to 13^th March 1839.
² Daniel O’Connell (1775-1847) was an Irish nationalist leader and social reformer.
³ William Lamb (1779-1848), 2^nd Viscount Melbourne, served as Prime Minister from 16^th July to 14^th November 1834, and from 18^th April 1835 to 30^th August 1841.
⁴ Charles Grant (1778-1866), 1^st Baron Glenelg, served as Secretary of State for War and the Colonies from 18^th April 1835 to 20^th February 1839.

The English naval officer and novelist Frederick Marryat (1792-1848) used the phrase in Poor Jack (London: Longman, Orme, Brown, Green, and Longmans, 1840):

“We have been thinking that, perhaps, you would have no objection to be a channel and river pilot; and if so, I have an old friend in that service, who, I think, may help you. What do you say?”
[…]
“It is the very thing that I should like,” replied I; “and many thanks to you, Anderson.”
“And it’s exactly what I should wish, also,” replied my father. “So that job’s jobbed, as the saying is.”

The phrase occurs in Easter Pieces, published in John Bull (London, England) of Sunday 26^th April 1840:

The King of Noland […] has just come from the christening of his daughter—Is-a-belle—the first fruits of his ten years’ marriage. As he right royally expresses himself, “that job’s jobbed.”