Float
Old English flotian (verb), of Germanic origin and related to fleet4, reinforced in Middle English by Old French floter, also from Germanic.
wiktionary
From Middle English floten, from Old English flotian(“to float”), from Proto-West Germanic *flotōn, from Proto-Germanic *flutōną(“to float”), from Proto-Indo-European *plewd-, *plew-(“to float, swim, fly”). Cognate with Saterland Frisian flotje(“to float”), West Frisian flotsje(“to float”), Dutch vlotten(“to float”), Middle Low German vloten, vlotten(“to float, swim”), German flötzen, flößen(“to float”), Swedish flotta(“to float”), Icelandic fljóta, Old English flēotan(“to float, swim”), Ancient Greek πλέω(pléō), Lithuanian plaukti, Russian пла́вать(plávatʹ), Latin plaustrum(“wagon, cart”). Compare flow, fleet.
etymonline
float (v.)
late Old English flotian "to rest on the surface of water" (intransitive; class II strong verb; past tense fleat, past participle floten), from Proto-Germanic *flotan "to float" (source also of Old Norse flota, Middle Dutch vloten, Old High German flozzan, German flössen), from PIE *plud-, extended form of root *pleu- "to flow."
Meaning "drift about, hover passively" is from c. 1300. Transitive sense of "to lift up, cause to float" (of water, etc.) is from c. 1600; that of "set (something) afloat" is from 1778 (originally of financial operations). Of motion through air, from 1630s. Meaning "hover dimly before the eyes" is from 1775. Related: Floated; floating. A floating rib (by 1802) is so called because the anterior ends are not connected to the rest.
float (n.)
apparently an early Middle English merger of three related Old English nouns, flota "boat, fleet," flote "troop, flock," flot "body of water, sea;" all from the source of float (v.). The early senses were the now-mostly-obsolete ones of the Old English words: "state of floating" (early 12c.), "swimming" (mid-13c.); "a fleet of ships; a company or troop" (c. 1300); "a stream, river" (early 14c.). From c. 1300 as an attachment for buoyancy on a fishing line or net; early 14c. as "raft." Meaning "platform on wheels used for displays in parades, etc." is from 1888, probably from earlier sense of "flat-bottomed boat" (1550s). As a type of fountain drink, by 1915.
Float.—An ade upon the top of which is floated a layer of grape juice, ginger ale, or in some cases a disher of fruit sherbet or ice cream. In the latter case it would be known as a "sherbet float" or an "ice-cream float." ["The Dispenser's Formulary: Or, Soda Water Guide," New York, 1915]
Few soda water dispensers know what is meant by a "Float Ice Cream Soda." This is not strange since the term is a coined one. By a "float ice cream soda" is meant a soda with the ice cream floating on top, thus making a most inviting appearance and impressing the customer that you are liberal with your ice cream, when you are not really giving any more than the fellow that mixes his ice cream "out of sight." [The Spatula, Boston, July, 1908]
