back: [OE] Back goes back to a prehistoric West and North Germanic *bakam, which was represented in several pre-medieval and medieval Germanic languages: Old High German bah, for example, and Old Norse bak. In most of them, however, it has been ousted by relatives of English ridge, originally ‘spine’ (such as German rücken and Swedish rygg), and only English retains back. => bacon[back etymology, back origin, 英语词源]