Fear of Short Names?
Formality is the fashion in American male names. I know boys named Thomas, but no young Toms; boys named Philip, but no young Phils. Lately, that avoidance of shortened names has jumped the fence, entering the world of short names.
The most common examples are the "just add n" names. These are names like Brycen and Colton, often chosen with the intention of calling the boys Bryce and Colt. Those one-syllable names are perfectly complete in themselves, but a lot of parents are skittish about printing a single syllable on the birth certificate so they add the beloved -n ending for a "formal" version.
The lengthening impulse is now getting bolder. The first step was surnames. Parents who wanted a little Finn turned Finnegan into a first name. Quinlan, Callahan and many more are following in...um, Finnegan's wake. (Look, it just happened, ok?)
Now consider the name Leviticus. The third book of Moses isn't traditionally a baby name, but it's starting to become one in the U.S. today. The popularity of the boy's name Leviticus has risen by 250% in the past decade. In part, that reflects a trend toward adoption of biblical words as names (Messiah, Genesis, etc.). But I don't think it's any coincidence that the sharp rise in Leviticus mirrors a sharp rise in the classic Bible name Levi -- up 300% in the same time period. Clocking in at just four little letters, Levi felt too lightweight for some parents, so they extended it.
Not convinced by that evidence? Try the name Leviathan. It's hard to imagine religious inspiration behind naming your son for the beast described in the Book of Isaiah as the twisted serpent to be killed at the end of time, and in Psalms as the monster whose heads were crushed by God and fed to the creatures of the wilderness. Isn't it more likely that the parents who have chosen the name in recent years -- 19 of them in 2011 -- thought of Leviathan as a formal source for Levi, much as Jonathan is for Jon? (Honestly, it does sound pretty cool.)
I understand the appeal of a name with formal and informal variations. Introducing yourself as Alexander makes a different impression from Alex, which in turn differs from Xander, Sasha or Sandy. If you adore the name Finnegan -- or Leviathan -- but like the idea of Finn or Levi for everyday use, more power to you. But don't let the brevity of Finn and Levi trick you into thinking they're not full, substantial names. In fact, it's those trim originals that are the true classics.