“Ten bagger” (or “tenbagger”) is a term coined by Wall Street stock investor Peter Lynch for a stock that’s worth ten times its original price. In baseball, a “two-bagger” is a double, a “three-bagger” is a triple and a “four-bagger’ is a home run, representing the “bags” or “bases.” A “ten bagger” investment is like a “home run” investment (a very successful one).
 
The term “tenbagger” has been cited in print since 1989.
     
   
Wikipedia: Ten bagger
Ten bagger is an investment term coined by Peter Lynch in his book One Up On Wall Street. This refers to an investment which is worth ten times its original purchase price, and was adapted from baseball where “bag” is a casual term for “base”, and extra-base hits like doubles, triples, and home runs are colloquially called two-, three-, or four-baggers.
   
Wikipedia: Peter Lynch
Peter Lynch (born January 19, 1944(1944-01-19)) is a Wall Street stock investor. He is currently a research consultant at Fidelity Investments. Lynch graduated from Boston College in 1965 and earned a Master of Business Administration from the Wharton School of the University of Pennsylvania in 1968.
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He also coined the phrase “ten bagger” in a financial context. This refers to an investment which is worth ten times its original purchase price and comes from baseball where “bags” or “bases” that a runner reaches are the measure of the success of a play. A “two bagger” would be a double, so by extension, two home runs and a double would be a “ten bagger”.
   
Google Books
One Up on Wall Street:
How to use what you already know to make money in the market
By Peter Lynch and John Rothschild
Philadelphia, PA: Running Press
1989
Pg. 17:
That’s where the tenbaggers (a Wall Street parlance meaning that your stock made ten times the money invested) come from, beyond the boundaries of accepted Wall Street cogitation.
Pg. 32:
STALKING THE TENBAGGER
The best place to begin looking for a tenbagger is (Pg. 33—ed.) close to home. Look in your own backyard. Dunkin’ Donuts, McDonald’s, Home Depot, The Limited, Southwest Airlines, and Staples—these were all started as local companies.
 
1 March 1989, Philadelphia (PA) Inquirer, “Family advice for the investor,” pg. D9:
It became a “ten-bagger,” a baseball-inspired term Lynch coined for a stock that scores even better than a home run.
 
10 March 1989, Washington (DC) Post, “Taking Stock of the Market” by Stan Hinden, pg. C4:
To further tempt us, Lynch regales us with tales of his “tenbaggers,” stocks in which he made 10 times his money, ordinary stocks such as Dunkin’ Donuts, ...
 
Google Books
Stock Market Rules:
70 of the most widely held investment axioms explained, examined, and exposed
By Michael D Sheimo
New York, NY: McGraw Hill
1999
Pg. 169:
TEN BAGGERS
Most investors would like to find what Peter Lynch fondly refers to as “ten baggers.” These are the superstocks with prices that seem to have no stopping point.