Don't rile the water. Do not stir up the water and make it muddy. The water is riled- muddy and unfit to drink. Common Norfolk expressions; also, a boy is riled (out of temper). I'sy, together, Joe Smith was regularly riled, is quite Norfolk. The American roil has the same meaning. A corruption of [em]broil. (French, brouiller; our broil.) The adjective rily, turbid, angry, is more common.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
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