Sense of "an engine or vehicle for pulling wagons or plows" is recorded by 1896, from earlier traction engine (1859). The meaning "powerful truck for pulling a freight trailer" is first found 1926; tractor-trailer as "combined motor-truck and trailer" is from 1914.
Among 100-odd new features in Excel 3.0 is a row of "buttons" on the screen called the Toolbar. Located under the pull-down menus, the Toolbar provides rapid access to frequently used commands. [Popular Science, April 1991.]
From 1650s as "moving from place to place;" by 1814 as "having the power of moving by itself. The noun meaning "engine which travels on rails by its own power" is from 1829, short for locomotive engine, which is attested from 1814. A locomotive engine used without rails was a traction engine, which became tractor.
1760, "young dog," shortened form of puppy (q.v.). Used earlier (from 1580s) for "conceited person," from the figurative sense of puppy. An English-Latin wordbook from late 15c. for Latin pupa gives English pup-bairn. Applied to the young of the fur seal from 1815. Used for "inexperienced person" by 1890.
Pup tent (also dog tent) as a type of small tent used in the military is from 1863. Sopwith pup, popular name of the Sopwith Scout Tractor airplane, is from 1917.