Javelin

Boyd’s Bible Dictionary:

A short, light spear
[ARMS.]

“252. Greaves Javelin” From Manners and Customs of the Bible:

1. Greaves were coverings for the legs. There are none represented on the Egyptian monuments, but they are seen on the Assyrian sculptures. They were of leather, wood, or, as in the case of Goliath, of brass, and were bound by thongs around the calves and above the ankles.
2. Kidon, here rendered “target,” is translated by the wordshield” in verse 45 of this chapter, and in Job 39:2323The quiver rattleth against him, the glittering spear and the shield. (Job 39:23); “spear” in Joshua 8:18, 2618And the Lord said unto Joshua, Stretch out the spear that is in thy hand toward Ai; for I will give it into thine hand. And Joshua stretched out the spear that he had in his hand toward the city. (Joshua 8:18)
26For Joshua drew not his hand back, wherewith he stretched out the spear, until he had utterly destroyed all the inhabitants of Ai. (Joshua 8:26)
; Job 41:2929Darts are counted as stubble: he laugheth at the shaking of a spear. (Job 41:29); Jeremiah 6:2323They shall lay hold on bow and spear; they are cruel, and have no mercy; their voice roareth like the sea; and they ride upon horses, set in array as men for war against thee, O daughter of Zion. (Jeremiah 6:23); and “lance” in Jeremiah 50:4242They shall hold the bow and the lance: they are cruel, and will not show mercy: their voice shall roar like the sea, and they shall ride upon horses, every one put in array, like a man to the battle, against thee, O daughter of Babylon. (Jeremiah 50:42). It was probably a light javelin, which could be easily hurled at an enemy. Some suppose it to have been decorated with a flag, like the lances of the Polish lancers. It would seem from this verse that when not in actual use it was carried on the back; for this is the meaning of “between the shoulders.” It was probably slung across he shoulders by means of a leathern strap.

“260. Fleeing From the Dart” From Manners and Customs of the Bible:

1 Samuel 19:1010And Saul sought to smite David even to the wall with the javelin; but he slipped away out of Saul's presence, and he smote the javelin into the wall: and David fled, and escaped that night. (1 Samuel 19:10). Saul sought to smite David even to the wall with the javelin; but he slipped away out of Saul’s presence, and he smote the javelin into the wall: and David fled, and escaped that night.
According to an ancient Asiatic custom, when a dart was thrown at a freedman, and he escaped from it by flight, he was thereby absolved from all allegiance to his master. Thus Saul by his murderous fury gave complete liberty to David, whose subsequent acts of war against the king could not be considered rebellion. From that hour he was no longer a subject of King Saul (See Kitto's Cyclopoedia of Biblical Literature, vol.1, p. 225).