'desasosiego' originates from Spanish, built from the prefix 'des-' (a negative or privative prefix meaning 'lack of' or 'undoing') plus 'asosiego' (related to 'sosiego', meaning 'calm' or 'quiet').

'desasosiego' developed in Spanish by prefixing 'des-' to earlier Spanish 'sosiego'/'asosiego' (Old Spanish forms like 'sosiego'), which itself came into Spanish from earlier Romance developments of Latin roots related to quietness or repose.

Initially it denoted the simple absence or opposite of 'sosiego' (calm), and over time it has come to be used broadly for feelings of unease, restlessness, or anxiety.