Let's Play The Name Game

Definition: an incredulous or habitually doubtful person

Doubting Thomas comes from the name of St. Thomas, the apostle who doubted the resurrection of Jesus. The name has been used to refer to an incredulous person for a number of centuries, dating back at least to the late 17th century. Thomas was not the only apostle to lend his name to an idiomatic term; Judas may be found in Judas goat, the name for an animal (often used figuratively) who leads other animals to a slaughterhouse or similarly unfortunate destination. 

To make yet a doubting Thomas believe the existence of no Popry in this codicle, let him thrust his hand into the side and looke upon the Prints of these things, in the body of the Church Reformed, he shall, or may be ascertained of its Innocency….
—William Annand, Mysterium Pietatis, 1671

Definition: 1. a member of the public or the community  2. the public or the community personified

No one knows what the Q in John Q Public actually means, due to the fact that the initial doesn’t really stand for anything. When the name began being used to refer to the collective public (in the early 20th century) we would occasionally find letters other than Q. stuck between the John and the Public. 

John J. Public is singing a new song these prohibitory days.
—The Atlanta Constitution (Atlanta, GA), 25 Nov. 1925

The belief that John G. Public is pretty well fed up with trick homers appears to be pretty general among the magnates, but some of course are expected to oppose any effort to change this rule.
—The Indiana Gazette (Indiana, PA), 18 Nov. 1930

The S. E. C. has no power to correct this evasion of the Act unless it obtains positive proof of the facts. Thus John X Public does not get the “inside dope” anticipated when the law was written.
—The Palm Beach Post (West Palm Beach, FL), 20 Feb. 1935

What is currently our earliest evidence for the word contains no middle initial at all. 

As usual, in all those European fights, it's old John Public who kicks in at the gate with the old two bits.
—The Washington Times (Washington, D.C), 7 Aug. 1914

Definition: an ordinary man; specifically: a blue-collar worker

Joe Six-Pack is one of the more recent additions to our stable of idiomatic words formed from first names, and is believed to have come from the stereotype of a six-pack of beer being the preferred libation of many blue-collar workers. Joe, much like John, is often used in conjunction with another word to designate a person of resoundingly average qualities: Joe Blow, Joe Bloggs, Joe Doakes, and Joe Schmo are just a few of the ways that our language has managed to insult those whose parents named them Joseph.

Coined by one of the area's livelier political informants, the picture is that of "Joe Six-Pack," a guy who works hard and wants to be left alone.
—Martin F. Nolan, The Boston Globe, 28 Aug. 1970

Definition: an autograph signature

John Hancock (1737-1793) was a governor of Massachusetts (twice), member of the Continental Congress, and signatory of the Declaration of Independence. It is for the last of these three roles that he is best remembered. His signature is dramatically large, dwarfing all the names surrounding it. It took a while to catch on, but by the late 19th century John Hancock was adopted as another word for signature.

Taking it for the gospel truth, the innocent seizes the pen and again writes his "John Hancock."
—Holmes County Republican (Millersburg, OH), 17 Nov. 1870

Definition: one that is by force of circumstances a center from which something undesirable spreads 

Typhoid Mary came into our language from the case of Mary Mallon, the asymptomatic carrier of the highly infectious disease typhoid. In the early 20th century Mallon was working in and around the New York City area as a cook, showing and experiencing no symptoms of typhoid herself, but infecting numerous others. She was twice placed in involuntary medical isolation (the second time for the remainder of her life). After she was initially found to have been responsible for a number of infections Mallon’s first name was combined with Typhoid, and used first to refer to actual typhoid carriers, and then took on a figurative meaning, in which it referred to one who spread any one of a number of undesirable things. 

It used to be thought water was the principal source of typhoid; but now that “typhoid Marys” have been discovered, who, while themselves immune, shed typhoid germs as a southern oak sheds wood ticks, the peril is different.
—Norwich Morning Bulletin (Norwich, CT), 29 Jul. 1909

Definition: alcoholic liquor personified

John Barleycorn is one of our older idiomatic names, dating in use back to at least the early 17th century. We know this because some intrepid soul in the 1620s published a song with the exceptionally catchy title of  A Pleasant New Ballad to Sing Both Even and Morne, of the Bloody Murther of Sir John Barley-corne (the criteria for what made a song title catchy were a bit different 400 years ago). 

A temperate man.
Sir John Barly-corne is no body with him.
Be merry and wise.
A feast without wine.
More for bread than beere.
Enough's as good as a feast.
Lick hony with your little-finger.
A light supper keeps cleane sheets.
—John Clarke, Proverbs English and Latine, 1639

Definition: a euphemistic expression of irritation or exasperation, often preceded by the or in

It is certain that there were people named Sam Hill before this name became a near synonym for tarnation, but it does not appear that any of these people were the cause of the name being adopted as a word in English. The explanation usually given for the etymology of sam hill is that it is a euphemism for hell.

…but when I walk on the deck, I see one sailor man have one wheel, which he turn round first au droit, to the right, and then turn him to the left, and I speak him, “Why for what you so moch labor always?”—and he say, “Sair, the dam ship steer like Sam Hill.” Well I not can understand, and then I go down in my chamber cabin, and I look in the dictionnaire of Johnson and Valker, and I not find Sam, but I ask the captain, and he laugh and say, “Sam one man’s name;” so I look and find Hill, one little mountain, but still I not understand what was Sam Hill.
The Evening Post (New York, NY), 12 Feb. 1830