An Etymological Dictionary of the German Language/Annotated/Sack
Sack, masculine, ‘sack, bag, pocket,’ from the equivalent Middle High German sac (genitive sackes), Old High German sac (genitive sacches), masculine; corresponding to the equivalent Gothic sakkus, masculine, Old Icelandic sekkr, masculine, Anglo-Saxon sœcc, masculine, English sack, and Dutch zak. A loanword from Latin saccus (Italian sacco, French and Old Irish sac), which came through the medium of Greek σάκκος, from the Hebrew and Phœnician sak. The Latin word seems to have been introduced into German, through commercial intercourse with Roman merchants, at a very early period (in Cæsar's time?), probably contemporaneously with Arche, Kiste, and Schrein.