Etymology
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hot dog (n.)

also hotdog, "sausage on a split roll," c. 1890, American English, from hot (adj.) + dog (n.). Many early references are in college student publications; later popularized, but probably not coined, by cartoonist T.A. "Tad" Dorgan (1877-1929). It is said in early explanations to echo a 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.

hot-dog, n. 1. One very proficient in certain things. 2. A hot sausage. 3. A hard student. 4. A conceited person. ["College Words and Phrases," in Dialect Notes, 1900]

Related: Hot-dogger; hot-dogging.

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hot air (n.)
"unsubstantiated statements, boastful talk," 1900, from hot (adj.) + air (n.1). The adjectival phrase hot-air (of balloons, etc.) is from 1813.
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dog-leg (adj.)

also dogleg, "bent like a dog's hind leg," 1843, earlier dog-legged (1703), which was used originally of a type of staircase which has no well hole and consists of two flights with or without winders. See dog (n.) + leg (n.).

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hot pants (n.)
"short-shorts," 1970, from hot (adj.) + pants (n.). Probably influenced by earlier sense of "sexual arousal" (1927).
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hot spot (n.)
also hotspot, 1888 as a skin irritation; 1931 as "nightclub;" 1938 in the firefighting sense; 1941 as "place of international conflict." See hot (adj.) + spot (n.).
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hot water (n.)
c. 1400, literal; 1530s in figurative sense of "trouble." See hot (adj.) + water (n.1). Hot-water bottle is from 1895.
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dog days (n.)

"period of dry, hot weather at the height of summer," 1530s, from Latin dies caniculares, the idea, though not the phrase, from Greek; so called because they occur around the time of the heliacal rising of Sirius, the Dog Star (kyōn seirios). Noted as the hottest and most unwholesome time of the year; often reckoned as July 3 to August 11, but variously calculated, depending on latitude and on whether the greater Dog-star (Sirius) or the lesser one (Procyon) is reckoned.

The heliacal rising of Sirius has shifted down the calendar with the precession of the equinoxes; in ancient Egypt c. 3000 B.C.E. it coincided with the summer solstice, which also was the new year and the beginning of the inundation of the Nile. The "dog" association apparently began here (the star's hieroglyph was a dog), but the reasons for it are now obscure.

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rat fink (n.)
also ratfink, 1963, teen slang, see rat (n.) + fink (n.). Popularized by, and perhaps coined by, U.S. custom car builder Ed "Big Daddy" Roth (1932-2001), who made a hot-rod comic character of it, supposedly to lampoon Mickey Mouse.
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lima bean (n.)
1756, associated with Lima, Peru, from which region the plant (Phaseolus lunatus) was introduced to Europe c. 1500. Among the earliest New World crops to be known in the Old World, Simmonds' "Dictionary of Trade" (1858) describes it as "esteemed," but it has the consistency of a diseased dog kidney.
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Dobermann pinscher (n.)

breed of domestic dog, originally used in police work, 1911 (as pincher Dobermann from 1907), named for Ludwig Dobermann, 19c. German dog-breeder in Thuringia. Pinscher "fox terrier" seems to be a 19c. borrowing from English pinch (see Kluge).

Der Kutscher aus gutem Hause verschafft sich, wie er kann und wenn er kann, einen ganz kleinen englischen Pinscher, der den Pferden sehr gut gut folgt und die großen Dänen von ehedem ersetzt hat, aus J.J. Rousseau's Zeit, der von dem dänischen Hunde umgerannt wurde, wie ihr wißt. ["Paris, oder, Das Buch der Hundert und Ein," Volume 6, Theodor Hell (pseud.), Potsdam, 1833]
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