Old English hat "hot, flaming, opposite of cold," used of the sun or air, of fire, of objects made hot; also "fervent, fierce, intense, excited," from Proto-Germanic *haita- (source also of Old Saxon and Old Frisian het, Old Norse heitr, Middle Dutch and Dutch heet, German heiß "hot," Gothic heito "heat of a fever"), of uncertain origin, perhaps related to Lithuanian kaisti "to grow hot;" both could be from a substratum word.

With a long vowel in Middle English (rhyming with boat, wrote) which shortened in modern English, perhaps from influence of comparative hotter. As an adverb, Old English hote.

Hot as "full of sexual desire, lustful" is from c. 1500; the sense of "inciting desire" is 18c. Taste sense of "pungent, acrid, biting" is from 1540s. Sense of "exciting, remarkable, very good" is 1895; that of "stolen" is first recorded 1925 (originally with overtones of "easily identified and difficult to dispose of"); that of "radioactive" is from 1942. Of jazz music or combos from 1924.

Hot flashes in the menopausal sense attested from 1887. Hot stuff for anything good or excellent is by 1889, American English. Hot seat is from 1933. Hot potato in figurative sense is from 1846 (from being baked in the fire coals and pulled out hot). Hot cake is from 1680s; to sell like hot cakes is from 1839.

The hot and cold in hide-and-seek or guessing games (19c.) are from hunting (1640s), with notion of tracking a scent. Hot and bothered is by 1921. Hot under the collar in the figurative sense is from 1895.

"passionate," 1590s; a relic of old medicine and medieval physiology theory; see hot (adj.) + blood (n.).

"short-shorts," 1970, from hot (adj.) + pants (n.). Probably influenced by earlier sense of "sexual arousal" (1927).

"hastily," c. 1300, from hot + foot (n.). As a verb in U.S. slang, from 1896. As the name of a prank played with matches, by 1934.

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

also hot rod, 1945, American English, from hot (adj.) + rod (n.), here apparently in a sense of "hunk of metal" (the cars also were called hot iron).

c. 1400, literal; 1530s in figurative sense of "trouble." See hot (adj.) + water (n.1). Hot-water bottle is from 1895.

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.).

"heated to full incandescence," 1820, from white (adj.) + hot (adj.). White heat is from 1710; figurative sense of "state of intense or extreme emotion" first recorded 1839.

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.