From the Latin habilis, 'easy to handle', itself derived from habere 'to handle'. And for those who think Nike had an original idea, also the root of the imperative injunction Habet! (just...HANDLE it!!!)
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While the word is much less common in everyday speech, the word
"habilitate" means "to make fit" or "to become suitable for certain
conditions". Therefore, to rehabilitate means "to make fit (or
suitable) again".