fleet (n.) Look up fleet at Dictionary.com
Old English fleot "a ship, raft, floating vessel," also, collectively, "means of sea travel; boats generally," from fleotan "to float, swim," from PIE *pleud-, extended form of root *pleu- "to flow."

Sense of "naval force, group of ships under one command" is in late Old English. The more usual Old English word was flota "a ship," also "a fleet; a sailor." The fleet for "the navy" is from 1712. The Old English word also meant "estuary, inlet, flow of water," especially the one into the Thames near Ludgate Hill, which lent its name to Fleet Street (home of newspaper and magazine houses, standing for "the English press" since 1882), Fleet prison (long used for debtors), etc.
fleet (v.) Look up fleet at Dictionary.com
Old English fleotan "to float; drift; flow, run (as water); swim; sail (of a ship)," from Proto-Germanic *fleutan (source also of Old Frisian fliata, Old Saxon fliotan "to flow," Old High German fliozzan "to float, flow," German fliessen "to flow, run, trickle" (as water), Old Norse fliota "to float, flow"), from PIE root *pleu- "to flow."

Meaning "to glide away like a stream, vanish imperceptibly" is from c. 1200; hence "to fade, to vanish" (1570s). Related: Fleeted; fleeting.
fleet (adj.) Look up fleet at Dictionary.com
"swift," 1520s, but probably older than the record; apparently from or cognate with Old Norse fliotr "swift," from Proto-Germanic *fleutaz, from PIE *pleud-, extended form of root *pleu- "to flow." Related: Fleetness.