From bull + pup. The firearms sense originated from firearm designers in the United States during the 1930s. The unconventional configuration of bullpup rifles was compared by analogy to bulldog puppies, which were considered "squat, ugly, but still aggressive and powerful"."
> Bulldog, also known as ‘Bulldozer’. An angular cartridge derringer patented by
Henry Hammond in 1866 and made by the Connecticut Arms Co. until
1868 in chamberings ranging from .22 Short rimfire to .50. The barrel was
released by a catch on the breech top and pivoted to the left to expose the
chamber.
> Bulldog A five-shot double-action swing-cylinder revolver designed by Douglas
McClenahan, and made in the U.S.A. by the Charter Arms Corporation in
.357 Magnum or .44 Special. Barrels may be 2.5 or 3 inches long, the latter
being discontinued in 1988. Finish may be blue or stainless steel, and some
guns (usually with ‘P’ suffix catalogue numbers) may be obtained with the
snubbed ‘Pocket Hammer’. They also have wraparound neoprene grips instead
of wood. See also ‘Police Bulldog’, ‘Target Bulldog’.
Bulldog Pug Introduced by Charter Arms in 1986, this is a variant of the
Bulldog with a 2.5in barrel, fixed sights, a shrouded ejector and a broad
hammer spur.
>Bulldog Tracker Another variant of the Charter Arms Bulldog, dating from
c. 1982–6 and 1989 to date, this .357 Magnum revolver has adjustable sights,
hand-filling wooden grips and barrels of 2.5–6 inches.
> Bulldozer A cartridge derringer patented in the U.S.A. by Henry Hammond,
better known as the ‘Bulldog’ (q.v.)
https://en.wikipedia.org/wiki/British_Bull_Dog_revolver
https://en.wiktionary.org/wiki/bullpup
"Etymology
From bull + pup. The firearms sense originated from firearm designers in the United States during the 1930s. The unconventional configuration of bullpup rifles was compared by analogy to bulldog puppies, which were considered "squat, ugly, but still aggressive and powerful"."