Old English gnæt "gnat, midge, small flying insect," earlier gneat, from Proto-Germanic *gnattaz (source also of Low German gnatte, German Gnitze); perhaps literally "biting insect" and related to gnaw.
The gnatte is a litil fflye, and hatte culex he soukeþ blood and haþ in his mouþ a pipe, as hit were a pricke. And is a-countid a-mong volatiles and greueþ slepinge men wiþ noyse & wiþ bytinge and wakeþ hem of here reste. [Bartholomew Glanville, "De proprietatibus rerum," c. 1240, translated by John of Trevisa c. 1398 ]
Gnat-catcher, insectivorous bird of the U.S. woodlands, is from 1823.
"nest, breeding place," especially the case or cell formed by an insect or spider for reception of its eggs, 1742, from Latin nidus "a nest," from Old Latin *nizdus (see nest (n.)). Figurative use by 1807. Classical plural is nidi.