benefit or interest (esp in the phrase for (someone'sorone's own) sake)
2.
the purpose of obtaining or achieving (esp in the phrase for the sake of (something))
3.
used in various exclamations of impatience, urgency, etc
for heaven's sake
for pete's sake
Word origin
C13 (in the phrase for the sake of, probably from legal usage): from Old English sacu lawsuit (hence, a cause); related to Old Norse sok, German Sache matter