The Hobbyhorse, or Dandy horse, was a human powered vehicle generally regarded as the early prototype for the bicycle. Invented by Baron Karl Drais, as the article above indicates, and patented in France in 1818, the vehicle function through the rider pushing along the ground via walking or running.
The name Dandy horse naturally comes from the Dandy set adopting it as a new craze and seen as a novelty of gentleman at leisure for at least a few years.
From Sportman’s Slang (1825):
