fish (n.)

"a vertebrate which has gills and fins adapting it for living in the water," Old English fisc "fish," from Proto-Germanic *fiskaz (source also of Old Saxon, Old Frisian, Old High German fisc, Old Norse fiskr, Middle Dutch visc, Dutch vis, German Fisch, Gothic fisks), perhaps from PIE root *pisk- "a fish." But Boutkan on phonetic grounds thinks it might be a northwestern Europe substratum word.

Popularly, since Old English, "any animal that lives entirely in the water," hence shellfish, starfish (an early 15c. manuscript has fishes bestiales for "water animals other than fishes"). The plural is fishes, but in a collective sense, or in reference to fish meat as food, the singular fishgenerally serves for a plural. In reference to the constellation Pisces from late 14c.

Fish (n.) for "person" is from 1750 with a faintly dismissive sense; earlier it was used in reference to a person considered desirable to "catch" (1722). Figurative sense of fish out of water "person in an unfamiliar and awkward situation" attested by 1610s. To drink like a fish is from 1744. Fish-story "incredible or extravagant narration" is attested by 1819, U.S. colloquial, from the tendency to exaggerate the size of the catch (or the one that got away).

Do not tell fish stories where the people know you; but particularly, don't tell them where they know the fish. ["Mark Twain," in "More Maxims of Mark" by Merle Johnson (1927)]

To have other fish to fry "other objects which invite or require attention" is from 1650s. Fish-eye as a type of lens is from 1961. Fish-and-chips is from 1876; fish-fingers from 1962.

fish (v.)

Old English fiscian "to fish, to catch or try to catch fish" (cognates: Old Norse fiska, Old High German fiscon, German fischen, Gothic fiskon), from the root of fish (n.). Related: Fished; fishing.

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Definitions of fish from WordNet
fish (v.)
seek indirectly;
fish for compliments
Synonyms: angle
fish (v.)
catch or try to catch fish or shellfish;
I like to go fishing on weekends
fish (n.)
any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills;
the shark is a large fish
in the living room there was a tank of colorful fish
fish (n.)
the flesh of fish used as food;
in Japan most fish is eaten raw
after the scare about foot-and-mouth disease a lot of people started eating fish instead of meat
they have a chef who specializes in fish
Fish (n.)
(astrology) a person who is born while the sun is in Pisces;
Synonyms: Pisces
Fish (n.)
the twelfth sign of the zodiac; the sun is in this sign from about February 19 to March 20;
Synonyms: Pisces / Pisces the Fishes