silver-bullet
'a bullet made of silver; a remedy which is very effective, almost magical’
Lexical development traced from the Tamil root:
silver + bullet < F. boulette ‘cannonball’ < boule < Lat. bulla ‘round thing’ + -et < O.F. -et,-ette < Vulgar Lat. -ittum/-itta < uht < -et < Tamil iṭṭu