The Latin term motus, meaning “a moving” or “motion,” is the progenitor of the Old French word motif, which survived unchanged into Modern French and was subsequently borrowed into English. Motif, in turn, inspired the English term motive and its variants. Here’s an introduction to the motif/motive family.
Motif, employed in French to mean “theme” or “dominant feature,” was adopted into English to serve the same purpose, pertaining to a recurring idea in a literary work. The Germans borrowed it, too, attaching the native word leit (meaning “lead,” synonymous with primary) to it to describe an element in a musical composition associated with and characteristic of a person, place, or thing; the term was popularized by discussions of Wagner’s operas. The ever-welcoming English language included leitmotiv in its repertoire in the 1870s, a few decades after motif was adopted.
However, motive, descended from the French term, dates from late medieval times and has spawned other words. Motive refers to an inward inclination to behave in a certain way or to take a specific action or course; it is less commonly employed as an adjective. (Interestingly, the connotation in a reference to someone’s motive for doing something is often a negative one; the word often implies scheming for selfish purposes.)
Automotive (motive joined with the Greek prefix meaning “self”) was coined to refer to a theoretical flying vehicle in the mid-nineteenth century and later pertained to horseless carriages; locomotive was started out as an adjective in the early 1600s but became associated with railroad technology 200 hundred years later, first in the phrase “locomotive engine” and soon thereafter as a noun itself.
Emotive began life as an adjective meaning “causing movement” and then acquired the connotation of “capable of emotion,” but its primary sense now, dating from early twentieth-century literary criticism, is “evoking emotions.” (The verb emote, meaning “to express emotions,” is a back-formation not from emotive but from the noun emotion.)
To motivate is to inspire or prompt action; the noun form is motivation.
