An Etymological Dictionary of the German Language/Annotated/Galgen
Galgen, masculine, ‘gallows, gibbet, crossbeam,’ from Middle High German galge, Old High German galgo, masculine, ‘gallows (also applied to the cross of Christ), frame over a well from which the bucket is hung to draw water.’ It corresponds to Old Saxon galgo, Dutch galg, Anglo-Saxon gealga, English gallows (the plural used as a singular, yet compare gallow-tree), Old Icelandic galge, ‘gallows,’ Gothic galga, masculine (applied to the cross of Christ, as also in all the other Old Teutonic dialects); a common Teutonic word, Teutonic galgan-, pre-Teutonic ghalgha-; compare Lithuanian żalga, feminine, ‘pole.’ Note the double sense of the Middle High German and Old High German word. Probably some such idea as a ‘long pliable rod’ is the starting-point of the various meanings of the cognates.