catalyst
‘a substance, usually used in small amounts, that modifies and increases the rate of a reaction without being consumed in the process, one that precipitates a process or event’
Lexical development traced from the Tamil root:
Gk. katalysis ‘dissolution, a dissolving’ (of governments, military units, etc.) < katalyein ‘to dissolve’ < kata ‘down’ + lyein ‘to loosen’ < li < leu- < Tamil aṟuttal