activate, actuate

Activate (17th century) originally meant 'to make active' (as in activate the lungs). It fell out of use for a time at the end of the 19th century, and was marked as obsolete in the first Old English (up to 1150)D. New uses in physics, chemistry, and other branches of science have brought it back into prominence and actuate (also 17th century in current meanings), once dominant, is now in decline (under 500 in the Old English (up to 1150)C). Activate (over 10,000 in the Old English (up to 1150)C) is the normal word in mechanical contexts such as burglar alarms, traffic lights, flight plans, and also occasionally in the context of human behaviour, where the choice is perhaps influenced by motivate (e.g. Are they activated by concern for public morality?). Actuate, which has a much higher proportion of passive uses with by than does activate, is less common in physical and mechanical contexts, and is generally restricted to less appealing abstract qualities such as anger, greed, jealousy, malice, etc.

(His opposition was actuated by a different and more compelling motive than that of her other relatives—David Cecil, 1948

the real objects that actuate our sentiments and passions—British English source, 2000 [Old English (up to 1150)C].

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