The use of middle names became popular here in New England in the late 18th and early 19th centuries—so popular that, allegedly, one gentleman asked his town clerk to insert middle initials into his children's birth records, to keep up with the current fashion.
Genealogists will often find the surname of an allied family hidden in a child's middle name: President John Quincy Adams was named for his great-grandfather, John Quincy; Franklin Delano Roosevelt's mother was Sara Delano. A middle name could also serve as a second given name, as with Presidents Thomas Woodrow Wilson and John Calvin Coolidge. This was sometimes done to distinguish a father from a son of the same name, but just as often was done to suit the preference of the bearer.
The genealogist should not make the mistake of assuming that a surname used as a child's middle name was always that of an allied family. It was common practice in the early Republic to name children for heroes of the Revolution and the Founding Fathers. Thousands of boys were named for George Washington, Thomas Jefferson, and Benjamin Franklin, and thousands more were given the middle name "LaFayette." Many children were named for regional celebrities—usually statesmen and war heroes—requiring that the genealogist be familiar with the historical background of the area and era she is researching. If a child was named for a living figure (as was my great-uncle Theodore Roosevelt Dunham, born in 1908), this is a sure indication of the parents' political or cultural interests at the time.
A few of the men for whom children were named in my corner of Maine:
Elbridge Gerry (signer of the Declaration from Massachusetts, and Vice President under Madison)I have also run across an Isaac Watts (named for an English preacher and hymn writer), a few John Miltons, and one Edgar Allan Poe. I have met in my research Albert Gallatins and Winfield Scotts, Martin Luthers and John Wesleys. But very few Benedict Arnolds.
Hannibal Hamlin (Vice President under Lincoln)
William King (first Governor of Maine)
Enoch Lincoln (Maine Governor and Representative to Congress)
Albion Keith Parris (Governor and Senator from Maine)
Virgil Delphini Parris (Congressman from Maine)