also hotdog, "sausage on a split roll," c.1890, popularized by cartoonist T.A. Dorgan. It is said to echo a 19c. suspicion (occasionally justified) that sausages contained dog meat. Meaning "someone particularly skilled or excellent" (with overtones of showing off) is from 1896. Connection between the two senses, if any, is unclear. Hot dog! as an exclamation of approval was in use by 1906.
A person who performs showy, often dangerous stunts, especially but not exclusively in sports; also, a showoff. For example, He was a shameless hot dog on the tennis court, smashing every ball, or She was a hot dog behind the wheel, screeching her wheels at every turn. The relation of this term to the edible hot dog is unknown. [Colloquial; c. 1900]
Also, hot diggety dog; hot diggety. An interjection expressing delight or enthusiasm, as in Hot dog! What a great gift, or Hot diggety! We got the best concert tickets after all. [Slang; c. 1900]