gnat (n.) Look up gnat at Dictionary.com
Old English gnætt "gnat, midge, mosquito," earlier gneat, used of various small, flying insects, from Proto-Germanic *gnattaz (cf. 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. [John of Trevisa, transl. of Bartholomew de Glanville's "De proprietatibus rerum," 1398]