The noun tycoon denotes a wealthy, powerful person in business or industry—cf. also fat cat.
It is from Japanese taikun, itself from Chinese ta, great, and chün, ruler.
The word tycoon was originally the title by which the shogun of Japan was described to foreigners from the mid-19th century to the end of the Tokugawa period, which was the last shogunate. The shogun was a hereditary commander-in-chief in feudal Japan. Because of the military power concentrated in his hands and the consequent weakness of the nominal head of state (i.e. the emperor, or mikado), the shogun was generally the real ruler of the country until feudalism was abolished in 1867. The following explanations are from The Encyclopædia Britannica (9th edition, 1881):
Prior to the recent revolution the foreign treaties were concluded with the ministers of the shôgun, at Yedo, under the erroneous impression that he was the emperor of Japan. The title of taikun (often misspelt tycoon) was then for the first time used; it means literally the “great ruler,” and was employed for the occasion by the Tokugawa officials to convey the impression that their chief was in reality the lord paramount. It is, however, worthy of note that even in these earlier treaties the title corresponding to “His Majesty” was never assumed by the shôgun. The actual position of this official remained unknown to the foreign envoys until 1868, when the British, Dutch, and French ministers proceeded to Kiôto, and there obtained from the mikado his formal ratification of the treaties already concluded with his powerful subject. Since that time all treaties with Western powers are made out in the name of the emperor of Japan. It was thus that the foreigners came prominently into notice at the time of the revolution, with which, however, beyond this they had really no connexion.
The word is first recorded in the diary of Townsend Harris (1804-78), first American Consul General and Minister to Japan:
Wednesday, October 28, 1857. To-day, I am told Ziogoon is not the proper appellation of their ruler, but that it is Tykoon. Ziogoon is literally “Generalissimo” while Tykoon means “Great Ruler.” The genius of the people shines out in this. For more than a year I have spoken and written Ziogoon when referring to their ruler, and they never gave me any explanation; but now, when I am on the eve of starting for Yedo, they give me the real word.
The fact that an official Japanese delegation visited the United States in 1860 popularised the word in American-English. All over the USA, newspapers reported on the visit, in particular on the reception held at the White House. Some newspapers also published satirical letters allegedly written by members of the Japanese delegation; for example, the following was published in The Daily Herald (Wilmington, North Carolina) on 26th May of that year:
From the Sacred City of Washington.
Most Esteemed Hakodadi:—[…]
The details of our reception by the American Tycoon you have in my former letter. He is called not Tycoon, but “President;” sometimes, however, by a strange analogy of language, “old coon.” I at first thought this an attempt to pronounce our Japanese phrase, but am assured that it is strictly idiomatic, and implies astuteness and age. It certainly seemed applicable to the head of the nation who received us.
We find it very difficult to comply with the demands of our sovereign, forbidding us to touch the women of this country. Not from any disposition on our part to disobey, but from their desire to seize us by the hands. They are apparently allowed here the greatest freedom, but it is only in appearance.—Every woman, married or single, is fastened in a cage of bamboo, or flexible steel, extending from the waist to the feet. This seems to be so arranged as to give them no uneasiness, but they are very much ashamed of it, and conceal it under so many coverings that it renders their appearance quite ludicrous. They are unrestricted as to the upper part of their persons, which they are permitted to expose as much as they wish. This they seem to avail themselves of, and on all occasions of high ceremony, wear very low dresses. As in all barbarous nations, they slit their ears and suspend from them ornaments of gold and silver. They also paint and powder themselves, and after greasing their hair, twist it into fantastic shapes and fasten it up with long pins and combs.—Some of them would be fine-looking, if they did not disfigure themselves by the hideous and vulgar custom of wearing eye brows and keeping their teeth white. Be assured, therefore, that we are in no danger of being captivated by their appearance; we feel nothing but regret that the barbarous and absurd customs of man should thus destroy the charms which cultivation and refinement would so much improve.
[…] None of the inhabitants do reverence by crawling on their bellies, except after the election of a new Tycoon, when those in search of office come to the central city and perform that ceremony. Those who are fortunate enough to meet with honor from the Tycoon seldom walk uprightly during their whole term of office. The unfortunate applicants become at once censors and spies upon the others, and their silence has to be bought at a high price. All public servants have their price, which rises or falls according to the necessities of the Tycoon.
Reception of the Japanese Embassy by President Buchanan in the East Room of the White House, Washington—from The Illustrated London News – 16th June 1860
The earliest instance of tycoon in the sense of a dominant or important person that I have found is from the New Orleans Daily Crescent (New Orleans, Louisiana) of 28th May 1860; an article explained why “Seward was defeated of the Black Republican nomination at Chicago” (Senator William Henry Seward (1801-72), one of the Republican Party’s foremost leaders, strongly opposed slavery; the term Black Republican originated as a pejorative appellation condemning the Republican Party as too favourable to the interests of slaves and hostile to the interests of slave-owners); according to the New Orleans Daily Crescent, one of the reasons for Seward’s defeat was:
He appropriated to himself, with entirely too much complacency, the position of master and “Tycoon” of the Black Republicans. He showed too plainly by his actions, as well as his speeches, that he felt himself their superior—and the assumption was galling to some of the other Black Republican Senators.
The Oxford English Dictionary (2nd edition, 1989) erroneously assumes that tycoon came to denote a dominant or important person from its use as a nickname of Abraham Lincoln (1809-65), president of the USA from 1861 to 1865. This is due to the fact that, in this dictionary, the earliest recorded quotation in which tycoon is not used in a Japanese context is from the diary of the American statesman John Hay (1838-1905), who wrote the following on 25th April 1861, during the American Civil War:
Gen Butler has sent an imploring request to the President to be allowed to bag the whole nest of traitorous Maryland Legislators and bring them in triumph here. This the Tycoon wishing to observe every comity even with a recusant State, forbade.
(from Inside Lincoln’s White House: The Complete Civil War Diary of John Hay (Southern Illinois University Press, 1997), edited by Michael Burlingame and John R. Turner Ettlinger)