Extreme, agonizing suffering of body or mind.
Extreme, agonizing suffering of body or mind — the high-water mark of mental pain.
The most acute, torturing member: it suggests torturing grief or dread, stronger than grief or sorrow (“cries of anguish,” “mental anguish”). It can point forward (dread of an impending horror), not only back at a loss, unlike grief or mourning; and it spans bodily as well as mental suffering. Its literal “tightness / choking” root reinforces the felt sense of being constricted. Foregrounds the writhing agony of the pain itself rather than despair's hopelessness.
Literal root is “tightness, choking.” c. 1200, from Old French anguisse “choking sensation, distress,” from Latin angustia “tightness, narrowness; straits,” from angere “to throttle, torment,” from PIE *angh- “tight, painfully constricted” — the same root as anger, anxious, and angst.
Continuous: from a concrete “tightness/choking” image to the figurative “distress, suffering” already in Old French and in English from c. 1200. The obsolete adjective anguishous once meant “full of wrath” as well as “anxious,” an older overlap with anger now shed. No reliable recent-generation shift.