Low of mood in the presence of loss. The feeling that something mattered and is missed — sorrow doing its honest work, not a malfunction.
Old English saed (sated, weary, having had enough), from Proto-Germanic *sadaz, related to Latin satis (enough); the word drifted from fullness and weariness to sorrow by the late Middle Ages.
Low mood in the presence of loss — proof that something mattered enough to be missed, and honest work rather than a malfunction.