An Etymological Dictionary of the German Language/Annotated/schüchtern
schüchtern, adjective, ‘shy, timid, bashful,’ early Modern High German only, allied to scheu, root skuh (skeuh)?. It may be connected even with the abnormal Old High German skihtîg, ‘shy,’ but we must assume the influence of Middle High German schiuhen on the stem vowel; see scheu.