Plural of 'able': people who are capable or skilled, or things that have ability.
From 'able' (capable) + plural suffix '-s'. In earlier English, 'able' could be used as a noun meaning 'one who is able,' though this usage is now archaic or dialectal.
You almost never hear 'ables' in modern English—we'd say 'able people' instead—but medieval texts used substantivized adjectives all the time, turning 'poor' into 'the poor' and 'able' into 'the ables.' It's a shortcut that has mostly faded out.
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