motor-boat (n.)

"one who or that which imparts motion," mid-15c., "controller, prime mover (in reference to God);" from Late Latin motor, literally "mover," agent noun from past-participle stem of Latin movere "to move" (from PIE root *meue- "to push away"). Sense of "agent or force that produces mechanical motion" is first recorded 1660s; that of "machine that supplies motive power" is from 1856. Motor-home is by 1966. Motor-scooter is from 1919. First record of slang motor-mouth "fast-talking person" is from 1970.

"small open vessel (smaller than a ship) used to cross waters, propelled by oars, a sail, or (later) an engine," Middle English bot, from Old English bat, from Proto-Germanic *bait- (source also of Old Norse batr, Dutch boot, German Boot), which is possibly from PIE root *bheid- "to split" (Watkins), if the notion is of making a boat by hollowing out a tree trunk or from split planking. Or it may be an extension of the name for some part of a ship.

French bateau "boat" is from Old English or Norse. Spanish batel, Italian battello, Medieval Latin batellus likewise probably are from Germanic languages. Of serving vessels resembling a boat, by 1680s (ship for "serving vessel or utensil shaped like a ship" is attested by 1520s). The image of being in the same boat "subject to similar challenges and difficulties" is by 1580s; to rock the boat "disturb stability" is from 1914.