錠
ジョウ
lock, fetters, shackles
JLPT1 G7 S16 F1934
定# fix (straight) in place + 金 metal. Originally, a metal spindle fixed in place. Later understood as *solder* (liquefied metal that fixes other objects in place) → *ingot*; (medicinal) *tablet* (← objects of prescribed or fixed shape). *Lock* is the result of reinterpreting the character as 定 fix in place + 金 metal → metallic device that fixes something in place.
[Full Kanji Etymology List]