Plural of heartburn; recurrent instances of a burning sensation in the chest or the emotional pain of deep resentment.
From 'heartburn,' which combines 'heart' (Old English 'heorte') with 'burn' (Old English 'beornan'). The term was used for both emotional and physical chest sensations historically.
Medieval doctors actually thought emotional anguish and acid reflux were related phenomena caused by the same imbalance of bodily humors—wrong, but it shows why we use 'heartburn' for both!
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