A widely cited incident involves when J. P. Morgan (1837-1913) was asked by someone what the market would do that day. “It will fluctuate, young man. It will fluctuate,” Morgan reportedly replied.
   
“It will fluctuate” is cited in print by at least 1934, but no contemporary citation has been found.
 
 
Wikipedia: J. P. Morgan
John Pierpont Morgan (April 17, 1837 – March 31, 1913) was an American financier, banker and art collector who dominated corporate finance and industrial consolidation during his time. In 1892 Morgan arranged the merger of Edison General Electric and Thompson-Houston Electric Company to form General Electric. After financing the creation of the Federal Steel Company he merged the Carnegie Steel Company and several other steel and iron businesses to form the United States Steel Corporation in 1901. He is widely credited with having saved or rescued the U.S. national economy in general—and the federal government in particular—on two separate occasions. He bequeathed much of his large art collection to the Metropolitan Museum of Art in New York City and to the Wadsworth Atheneum of Hartford, Connecticut. He died in Rome, Italy, in 1913 at the age of 75, leaving his fortune and business to his son, John Pierpont (“Jack”) Morgan, Jr.
 
Middletown Times Herald (Newspaper) - February 28, 1934, Middletown,...
Subscription - Middletown Times Herald - NewspaperArchie - Feb 28, 1934
... Morgan the when someone asked him what the stock market was going to do I can tell you exactly what it will do for years to he said It will fluctuate ...
   
23 January 1958, Morgantown (WV) Post, “Stock Market Brokers Are Wise in Ways,” pg. 19, col. 1:
NEW YORK (UP)—Well, what’s the stock market going to do today?
 
To that question market men always used to say: “It will open at 10 a.m. and close at 3 p.m.” They revised that statement some years ago to read “open at 10 a.m. and close at 3:30 p.m.”
 
And, of course, J.P. Morgan, the elder, always used to reply to the query: “It will fluctuate.”
     
Time magazine
A Long Look Upward
Friday, Aug. 19, 1966
Wall Street runs two ways—up and down. This fact was recognized long ago by one of the Street’s alltime moguls, J. Pierpont Morgan. When asked by a brash young investor for a forecast about how the market would go, Morgan glared down his generously endowed nose, bristled his mustache, and replied: “It will fluctuate, young man. It will fluctuate.”
     
13 November 1972, New York (NY) Times, pg.  34 ad:
When asked his opinion of the direction of the stock market, J. P. Morgan is reputed to have said: “It will fluctuate.”
(Harry Rothman clothing—ed.)
 
6 July 1975, New York (NY) Times, “On Which Side of Options Lie Profits?” by Simeon H. F. Goldstein, pg. 108:
J. P. Morgan, when asked what the market will do, is said to have replied that “it will fluctuate”. This is usually regarded as an example of an extremely safe prediction.