Why do you think the AUTHOR chose a particular name for the visitor?It is a story written by H.H Munro
The story "The Open Window" by H.H. Munro, also known as "Saki", is that of a man named Mr. Frampton Nuttel, who visits the home of Mrs. Sappleton to spend sometime curing himself from a case of the nerves that left him somewhat impaired.
Mrs. Sappleton's niece, Vera, tells Mr. Nuttel a story that is meant to scare him, making him actually suffer another meltdown and run away from the house.
Saki is particular in naming his characters and some of his works demonstrate as much. In this case, the name of Frampton Nuttel is a bit disparate, and remind us of words such as frumpy-looking, crazy, and different. The name suggests itself to be strange; just as strange as Mr. Nuttel is, himself.
Since we do not know what exactly causes Mr. Nuttel's first breakdown we can only assume that he is, by nature, a somewhat weird individual. From his actions, we know that he is quirky and nervous. Therefore, his name is supposed to sound as funny as Mr. Nuttel, perhaps, looks in the eyes of the mischievous Vera.