Heat, fever, or burning sensation; boiling or surging motion (from Latin, archaic in English).
Direct from Latin 'aestus' (heat, tide, surge, boiling). An early borrowing that influenced many English words about tidal and thermal phenomena.
Latin 'aestus' gave English a whole family of words—estuary, estrange, and others—all carrying the sense of disturbance, heat, or agitation that Romans observed in nature.
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