sakeyoudaoicibaDictYouDict[sake 词源字典]
sake: English has two nouns sake. The older, now used only in the expression for the sake of, was originally an independent fully-fledged noun, with a range of meanings including ‘strife’, ‘guilt’, and ‘lawsuit’ [OE]. Its use in for the sake of, which emerged in the 13th century, probably arose out of its legal usage, and thus denoted originally ‘on behalf of a litigant’s case in a lawsuit’.

The word itself came from a prehistoric Germanic *sakō ‘affair, thing, charge, accusation’, which also produced German sache ‘affair, subject, lawsuit’. It is also represented in English forsake [OE], which etymologically means ‘accuse, quarrel with’, hence ‘decline’, and finally ‘give up’; keepsake [18], etymologically something that is kept for the ‘sake’ of the giver; and namesake [17], which probably arose from the notion of two people being linked or associated for the ‘sake’ of their names. Seek is a distant relation. Sake, or saki, ‘rice wine’ [17] was borrowed from Japanese, where it literally means ‘alcohol’.

=> forsake, keepsake, namesake, seek, seize[sake etymology, sake origin, 英语词源]
sake (n.2)youdaoicibaDictYouDict
"Japanese rice liquor," 1680s, from Japanese sake, literally "alcohol."
sake (n.1)youdaoicibaDictYouDict
"purpose," Old English sacu "a cause at law, crime, dispute, guilt," from Proto-Germanic *sako "affair, thing, charge, accusation" (cognates: Old Norse sök "charge, lawsuit, effect, cause," Old Frisian seke "strife, dispute, matter, thing," Dutch zaak "lawsuit, cause, sake, thing," German Sache "thing, matter, affair, cause"), from PIE root *sag- "to investigate, seek out" (cognates: Old English secan, Gothic sokjan "to seek;" see seek).

Much of the word's original meaning has been taken over by case (n.1), cause (n.), and it survives largely in phrases for the sake of (early 13c.) and for _______'s sake (c. 1300, originally for God's sake), both probably are from Norse, as these forms have not been found in Old English.