mov

The root mov traces back to a single Latin verb, movēre, "to move" — to shift something from one place to another. From this one verb, three slightly different shapes entered English, and once you can see all three as the same root wearing different clothes, a huge family of words clicks into place.

mov- is the present stem, closest to the original verb. It gives the plainest words: move, movement, remove (re- 'back/away' + move = move away), movable, mover, and the everyday movie — short for 'moving picture.'

mot- comes from the past participle mōtus, "moved." Latin loved building nouns and later words on the past participle, so this form is the most productive of the three. From mōtus we get motion (the act of moving), motor (a machine that produces movement), and a whole prefix series: promote (pro- 'forward' + mot = move forward → raise in rank, push a product), demote (de- 'down' + mot = move down in rank), remote (re- 'back/away' + mot = moved far away), and emotion (e-/ex- 'out' + mot = a stirring moved out of you). Notice how mot- carries the metaphors: emotion and promotion are not about physical travel at all, yet both are literally 'movings.'

mob- comes from Latin mōbilis (movēbilis), "able to be moved." This gives mobile (movable, and by extension the mobile phone you carry around), mobility, mobilize (set people or troops in motion), automobile (auto- 'self' + mobile = a self-moving vehicle), and — the surprise member — mob. A mob is short for the Latin phrase mobile vulgus, "the movable / fickle crowd," the common people who could be stirred and swayed; English clipped it down to mob, an unstable, easily-moved crowd.

The through-line of the whole family is the leap from physical to emotional. To move someone is to shift their feelings; an emotion is a feeling that 'moved out' into the open; a moving story stirs you; a motive is the inner thing that moves you to act. Whenever a mov/mot/mob word seems abstract, ask: what is being moved — a body, a rank, or a feeling?