Snicklefritz is a funny name. Schnickel is a funny (but real) name, and Fritz is a... name. Put them together and you have a Particularly Amusing Appellation. While there may very well be people named Snicklefritz1, it is usually used as a joke name.
But it didn't start out that way; Snicklefritz was originally used in Pennsylvania Dutch Country, where Snicklefritz is an affectionate name for a mischievous or overly talkative child.
Snicklefritz has been used in this manner for generations, and the origin has been lost in the mists of time. It is apparently original to the Pennsylvania Dutch, with no direct German root2. But these days it seeps into mainstream English in various (technically incorrect) contexts -- most often as a random silly name. Because so many people are called a Snicklefritz as a child, it is also a common nickname. Being rather cutesy, it is frequently used as a name for pets.
Snicklefritz is often written as 'Schnicklefritz'. There are, as you might expect, a large number of variations in the spelling of this word, and I will not attempt to list all the possible variations here. Schnickelfritz was the name of a somewhat popular comedy band in the 1930s, which may be the origin of its comparative popularity. Even so, 'Snicklefritz' is overwhelmingly the most popular spelling.
If you enjoyed this word, you might also enjoy the Pennsylvania Dutch words wunderfitz,
nichtsnutz, and bloppermowl.
1. I haven't found any reliable references to any real Snicklefritzs, but there are a few people on Facebook and Myspace who would like you believe that they are named Snicklefritz. I don't trust these people.
2. One theory is that it comes from the German slang words Schnickel or Schniggel, meaning a little boy's penis, plus the name Fritz. I don't trust this theory.