Etymology
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Mickey Finn 

"drink laced with chloral hydrate," by 1918. Mickey Finn was used from the 1880s as the name of the main character in a series of popular humorous Irish-American stories published by New York Sun staff writer Ernest Jarrold (1848-1912), who sometimes also used it as his pen-name. Perhaps there is a connection.

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Finn (n.)

"native or inhabitant of Finland; a member of the Finnic race,"  Old English finnas, from Old Norse finnr, the Norsemen's name for the Suomi. Some suggest a connection with fen. Attested in Tacitus as Fenni. Finlander in English is from 1727.

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Mickey Mouse 

cartoon mouse character created 1928 by U.S. animator Walt Disney (1901-1966). As an adjective meaning "small and worthless, petty, inconsequential" it was in use by 1951, perhaps from the popularity of the cheaply made Mickey Mouse wristwatch; it was used by 1935 in reference to mediocre dance-band music, based on the type of tunes played as background in cartoon films.

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Finnish (adj.)

"of or pertaining to Finland or its inhabitants," c. 1790, from Finn + -ish. Earlier was Finnic (1660s as a noun, in reference to the language). Related: Finno-.

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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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hog (v.)
"to appropriate greedily," 1884, U.S. slang (first attested in "Huck Finn"), from hog (n.). Earlier it meant "Cause to form a horizontal arch" (like the back of a hog), 1798, and "cut a horse's mane short" (so it bristles like a hog's back), 1769. Related: Hogged; hogging.
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fin (n.)
Old English finn "fin," from Proto-Germanic *finno (source also of Middle Low German vinne, Dutch vin), perhaps from Latin pinna "feather, wing" (see pin (n.)); or, less likely, from Latin spina "thorn, spine" (see spine).

U.S. underworld slang sense of "$5 bill" is 1925, from Yiddish finif "five," from German fünf (from PIE root *penkwe- "five") and thus unrelated. The same word had been used in England in 1868 to mean "five pound note" (earlier finnip, 1839).
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Samoyed (n.)

Siberian Mongolian people, 1580s, from Russian samoyed (11c.), traditionally literally "self-eaters," i.e. "cannibals" (the first element cognate with same, the second with eat), but this might be Russian folk etymology of a native name:

The common Russian etymology of the name Samoyed, meaning "self-eater," deepened the Russians' already exotic image of far-northerners. The most probable linguistic origin of Samoyed, however, is from the Saami — saam-edne, "land of the people" [Andrei V. Golovnev and Gail Osherenko, "Siberian Survival: The Nenets and Their Story," Cornell University, 1999]

Which would make the name a variant of Suomi "Finn." The native name is Nenets. As a language name by 1829. As the name of a type of dog (once used as a working dog in the Arctic) it is attested from 1889 (Samoyed dog).

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