"new convert," 15c., from French catéchumène, from Church Latin catechumenus, from Greek katekhoumenos "one being instructed," passive present participle of katekhein (see catechesis).
1960 as a frame fitted to a tractor to hold tools; from tool (n.) + bar (n.1). Computer sense is attested from 1991.
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.]