fishnet 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 fish generally 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 (a fisshe out of the see in the same sense is from mid-15c.). To drink like a fish is from 1744. 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.

Old English net "open textile fabric tied or woven with a mesh for catching fish, birds, or wild animals alive; network; spider web," also figuratively, "moral or mental snare or trap," from Proto-Germanic *natjo- (source also of Old Saxon net, Old Frisian nette, Old Norse, Dutch net, Swedish nät, Old High German nezzi, German Netz, Gothic nati "net"), perhaps originally "something knotted," from PIE root *ned- "to bind, tie." But Boutkan says it has no clear IE etymology and implies it might be a substrate word.

From late Old English as "light, open woven fabric used as protection from annoying insects." From late 15c. as "light, open mesh bag for the hair."

Proto-Indo-European root meaning "a fish."

It forms all or part of: fish; fishnet; grampus; piscatory; Pisces; piscine; porpoise.

It is the hypothetical source of/evidence for its existence is provided by: Latin piscis (source of Italian pesce, French poisson, Spanish pez, Welsh pysgodyn, Breton pesk); Old Irish iasc; Old English fisc, Old Norse fiskr, Gothic fisks.