https://en.wikipedia.org/wiki/Cornish_game_hen

"a young immature chicken (less than five weeks of age), weighing not more than two pounds ready-to-cook weight, which was prepared from a Cornish chicken or the progeny of a Cornish chicken crossed with another breed of chicken"

http://www.fsis.usda.gov/wps/wcm/connect/fsis-content/fsis-q...

https://www.law.cornell.edu/cfr/text/9/381.170

Current class definitions state that a bird labeled as a Rock Cornish-type chicken must be ``the progeny of a cross between a purebred Cornish and a purebred Rock chicken'' (9 CFR 381.170(a)(1)(ii)), or ``a Cornish chicken or the progeny of a Cornish chicken crossed with another breed of chicken'' (9 CFR 381.170(a)(1)(i)). While this statement was appropriate when these chickens were originally developed over 40 years ago, today it is doubtful that any purebred Cornish or Rock lines exist in commercial chicken production. The names ``Rock Cornish game hen'' and ``Cornish game hen'' are now used to identify a very young, very small, whole chicken that is marketed as an individual serving. Although the names refer to hens, either sex can be used since birds of this class are sexually immature. The names ``Rock Cornish fryer,'' ``Rock Cornish roaster,'' and ``Rock Cornish hen'' are no longer meaningful because these birds cannot be reliably distinguished on the basis of progeny from other existing classes. Therefore, the Agency is proposing to define the Rock Cornish game hen or Cornish game hen class only in terms of age and weight and to delete the class of Rock Cornish fryer, roaster, and hen.

Also of interest

http://www.fsis.usda.gov/OPPDE/rdad/FRPubs/2007-0048F.htm

Cornish Game Hens Comment: One comment from a trade association stated that the term ``hen'' as used in the ``Rock Cornish game hen'' or ``Cornish game hen'' class may be misleading because the term hen implies that these birds are female while the definition states that the birds may be of either sex. The comment suggested that FSIS change the name of this poultry class to ``Rock Cornish game bird'' or ``Cornish game bird.'' Another comment from a poultry producer said that the proposed ``Cornish hen'' definition is inaccurate because it allows industry to call a bird that is not necessarily Cornish, and not necessarily a hen, a ``Cornish hen.'' The comment suggested that FSIS add a definition for ``poussin'' to describe the next youngest bird than the ``Cornish hen'' if the Agency decides to keep the term Cornish hen. The comment suggested that USDA review the literature produced by the North American Meat Processors Association (NAMP) as it applies to usage of the term ``poussin.'' According to the commenter, because USDA is attempting to have its regulations reflect usage in the poultry industry, it must consider not just the production level, but also the market. Response: FSIS disagrees that the terms ``Rock Cornish game hen'' or ``Cornish game hen'' are misleading to consumers and that the Agency should change the name of the class to ``Rock Cornish game bird'' or ``Cornish game bird.'' The existing terms for this poultry class, which provides for the use of the term ``hen'' for young immature chickens of either sex, has been in place since FSIS established this poultry class definition. The term ``hen'' can be used for immature chickens of either sex because birds of this class are sexually immature. FSIS is not aware of any data to support that consumers are misled with the reference to ``hen'' in these terms. Changing the name of the class is likely to spur confusion. FSIS also disagrees that the proposed ``Cornish hen'' definition is inaccurate because it allows industry to call a bird that is not necessarily Cornish, and not necessarily a hen, a ``Cornish hen.'' The existing standards in FSIS' regulations do specify that a Cornish chicken be the progeny of a Cornish chicken crossed with another breed of chicken. However, FSIS continues to believe that it is doubtful that any purebred Cornish lines currently exist in commercial chicken production today and, therefore, the birds cannot be reliably distinguished on the basis of progeny. FSIS also disagrees that it should add a new poultry class that would define poussin. The poultry classes in 9 CFR 381.170 represent poultry that are typically marketed to consumers and are more broadly used than the standards for poussin in NAMP's Poultry Buyers Guide.