Each week , we tell the story of words and expressions used in American English . Our expression today is “the real McCoy .” If a person tells you that something is "the real McCoy ,” they are telling you that it is the real thing . It is not a copy or replacement . There is nothing false about “the real McCoy .” And , not only is it the real thing , it is the best version that exists . As usual , word experts do not agree on how this expression came into common use . A popular belief is that it is connected to Charles “Kid ” McCoy , a famous boxer of the past . During the 1800s , he was a one-time world champion . His real name was Norman Selby . Word historians also cannot agree on which Selby story is the origin of “the real McCoy .” One explanation goes like this : McCoy was having a drink in a bar with a woman friend . As the story goes , a man at the bar insulted McCoy by calling him a liar . He said he was not the famous prize-fighter . So , McCoy knocked him out with one hit . When the man came to his senses he called out , “That was the real McCoy !” The second version of the Kid McCoy story is much less flattering to the boxer . McCoy was accused of throwing many fights . To throw a fight means to lose on purpose for money . So , sportswriters would ask , “Who is going to show up for the boxing match ? The boxer who throws the fight or the real McCoy ?” However , there are other explanations for “the real McCoy .” One story takes us back to the days of Prohibition in the United States (1920-1933 ). During this time , it was illegal to sell alcohol . That , however , did not stop people from selling it . And many people sold low quality alcohol . As this story goes , there was one dealer who was honest . His name was Bill -- you guessed it -- McCoy . He refused to sell bad alcohol . Over time , his product became recognized as the best . It was called “the real McCoy .” The expression made it through the days of Prohibition and soon became a general term . But not so fast . Yet another possible explanation is from Canada . Canadian inventor Elijah McCoy made a successful machine for keeping train engines running smoothly . He patented his design in 1872 . But that did not stop others from copying it . These copies were all inferior , or not as good . So , railroad engineers would request the patented design by name . They wanted “the real McCoy ” system for their trains . Similar expressions include “the real deal ” and the “genuine article .” The adjective honest-to-goodness means the same thing . Now , let's hear these expression used in a short dialogue . And it should be . I paid enough for it !" "I'm afraid to ask … but how much did it cost ?" "That is a lot of money . But like you said it's the genuine article ." "Yep , you get what you pay for . There are many copies out there . So , you have to be careful ." The only way to really buy the Banana Book Pro is at the Banana store . That is where you bought it , isn't it ?" I bought it from a guy selling them out of his car . But he promised that it was an honest-to-goodness Banana Book Pro . He showed me the paperwork and everything ." I'm sure it's the real deal . Do you mind if I see the … uh oh , sorry , the logo just fell off . It's a good thing you have the paperwork ." Is the Banana Book Pro the real McCoy ? We may never know . And we may never know which story , if any of them , truly explains “the real McCoy .”