Smith's Bible Dictionary (1863)
(1 Samuel 5:18,22; 23:13; 1 Chronicles 11:15; 14:9; Isaiah 17:5) also in (Joshua 15:8) and Josh 18:16 It is translated in the Authorized Version “the valley of the giants,” a spot which was the scene of some of David’s most remarkable adventures. He twice encountered and defeated the Philistines there. (2 Samuel 5:17-25; 23:13) etc. Since the latter part of the sixteenth century the name has been attached to the upland plain which stretches south of Jerusalem and is crossed by the road to Bethlehem—the el Buk’ah of the modern Arabs.
(This valley begins near the valley of Hinnom, southwest of Jerusalem extending toward Bethlehem. It is about a mile long, with hills on either side. ) Tobler, however, in his last investigations conclusively adopts the Wady Der Jasin, on the northwest of Jerusalem. The valley appears to derive its name from the ancient nation of the Rephaim.