'anguishously' originates from Middle English, from the adjective 'anguishous,' ultimately from Old French 'angoisseus,' which traces back to Latin 'angustia' meaning 'narrowness; distress' and the verb 'anguere' meaning 'to constrict, to distress.'

'anguisshously' in Middle English developed from 'anguisshous' (adj.), influenced by Anglo-Norman, and later standardized in spelling to 'anguishously' in Early Modern English.

Initially, it meant 'in a manner full of anguish or causing anguish,' and over time the form became archaic while the sense survives in 'anguishedly' or phrases like 'in anguish.'