n. (esp. for the sake of or for one's sake) 1 out of consideration for; in the interest of; because of; owing to (for my own sake as well as yours). 2 in order to please, honour, get, or keep (for the sake of uniformity). for Christ's (or God's or goodness' or Heaven's or Pete's etc.) sake an expression of urgency, impatience, supplication, anger, etc. for old times' sake in memory of former times.
[ OE sacu contention, charge, fault, sake f. Gmc ]