An Etymological Dictionary of the German Language/Annotated/siech
siech, adjective, ‘sickly, infirm,’ from Middle High German siech, Old High German sioh (hh), adjective, ‘sick’; corresponding to Old Saxon siok, Dutch ziek, Anglo-Saxon seóc, English sick, Old Icelandic sjúkr, Gothic siuks, ‘sick.’ The Old Teutonic term for ‘sick, ill,’ compared with the Modern German word krank; compare the difference in meaning between Modern High German siech and Seuche. To this Sucht is allied (and schwach?), as well as Gothic siukan, strong verb, ‘to be weak.’ A pre-Teutonic root sug is wanting.