An Etymological Dictionary of the German Language/Annotated/Geist
Geist, masculine, ‘spirit, genius, spectre,’ from Middle High German and Old High German geist, masculine, ‘spirit (in contrast to body), supernatural being’; corresponding to Old Saxon gêst, Dutch geist, Anglo-Saxon gâst (gœ̂st), English ghost; common to Teutonic in the same sense, but in Gothic ahma (see achten). The primary meaning of the word (‘agitation’?) is not quite certain; yet Icelandic geisa, ‘to rage’ (of fire, passion), and Gothic us-gaisjan, ‘to enrage,’ seem to be allied. Respecting the dental suffix of the Teutonic Geist (pre-Teutonic ghaisdos), note the Sanscrit root hîḍ (from hizd), ‘to get angry,’ hêḍas, neuter, ‘anger,’ to which English aghast also corresponds.