An Etymological Dictionary of the German Language/Hengst
Hengst, m., ‘stallion,’ from MidHG. hęngest, OHG. hęngist, m., ‘gelding, horse (generally),’ comp. Du. hengst, m., ‘stallion,’ AS. hęngest, m., ‘male horse (generally),’ obsolete at the beginning of the MidE. period; OIc. hestr (from *hinhistr), m., ‘stallion, horse (generally).’ The earlier meaning of the HG. word was equus castratus, and by the adoption of the general term Pferd, ‘horse,’ the word obtained in ModHG. (from the 15th cent.) as ‘ungelded, male horse.’ In Goth. probably *hangists. The attempt to explain the word etymologically has not yet been successful; comp. Lith. szankus, ‘nimble’ (of horses)?, or Lith. kinkýti, ‘to put (horses) to’?.