An Etymological Dictionary of the German Language/Annotated/spähen
spähen, verb, ‘to spy,’ from the equivalent Middle High German spëhen, Old High German spëhôn. This word and the Old High German and Old Saxon adjective spâhi, Middle High German spœhe, ‘prudent, skilful’ (and Dutch bespieden, ‘to spy’?), are the sole relics of the Old Teutonic root speh, ‘to see,’ which, through Latin spec in speculum, conspicio, adspectus, as well as through Sanscrit spaç, ‘to see’ (Greek σκέπ-τω for *σπέκτω?), is proved to be primitively Aryan (Aryan root spek). From the Teutonic cognates those of Italian spiare, French épier, ‘to spy out’ (Italian spione, French espion, ‘spy,’ whence English spy), were borrowed at an early period.