Archaic KJV Word
Target
Modern equivalent: shield
What Was Lost
Goliath's defensive armor. The target of brass between Goliath's shoulders was a small shield protecting his neck and upper back -- a piece of armor, not something David aimed at. Modern readers picture a bullseye on Goliath's back, which, while poetically fitting, reverses the meaning entirely.
Closest Survivor in Modern English
targe (Scottish English preserves the shield meaning)
Peak Usage (1611)
KJV 1 Samuel 17:6 -- 'He had a target of brass between his shoulders' (describing Goliath's armor)
Died ~1750 (the 'shield' meaning died)
Shifted from 'a small shield/buckler' (Old French targette, diminutive of targe 'shield') to 'something aimed at,' inverting a word of defense into a word of attack.
What Replaced It
“shield”
Generic; target-as-shield was a specific type -- small, round, carried between the shoulders
“buckler”
Also archaic; both words for small defensive shields faded from common use