puppy or puppy dog.
A silly, vain, inane, or especially juvenile young man.
Even as full adults, dogs retain the characteristics of the young in the “wild” species from which they derive, in this case, wolves. In comparison with mature wolves, full-grown dogs have shorter snouts and larger eyes, which makes them look much like wolf pups. Behavior is also more like that of wolf pups: dogs remain playful throughout their lives. Being compared to a puppy is not simply to be described as young, but to be equated with the most juvenile stage of development of a species where even the adults aren't really grown ups.
The Century Dictionary says that this term for a small or young dog derives from its being “petted as a doll or a puppet.” Perhaps that is why Venezualan President Hugo Chavez called Mexico President Vicente Fox the “perrito,” or puppy dog, of the U.S.
1. Whitney, William Dwight and Benjamin E. Smith. 1914. The Century Dictionary and Cyclopedia; with a New Atlas of the World. New York: Century Co. Accessed from: http:// www.global-language.com/ century/.
2. Chávez Insiste En Criticar a Fox Por Debate De Cumbre De Las Américas. 2005. el universal.com. el universal.com. Accessed Jan 15 2006 from http:// internacional.eluniversal.com/ 2005/11/13/pol_ava_13A631501.shtml.