'quixotic' originates from Spanish, specifically the name 'Quixote' (from the title character of Cervantes's 'Don Quixote'), where 'Quixote' represented a romantic, chivalrous but impractical figure.

'quixotic' changed from the Spanish name 'Quijote'/'Quixote' (the character) and was adopted into English as the adjective 'quixotic' (formed by adding the suffix '-ic' to the name) to describe similar behavior.

Initially it meant 'like Don Quixote' (resembling the character's romantic, impractical actions), but over time it evolved into the broader modern meaning of 'excessively idealistic; unrealistic.'