Why is the ninth month called September?
1650s, "dissolution," from Latinized form of Greek katalysis "dissolution, a dissolving" (of governments, military units, etc.), from katalyein "to dissolve," from kata- "down" (or "completely"), see cata-, + lyein "to loosen" (see lose). Chemical sense "change caused by an agent which itself remains unchanged" is attested from 1836, introduced by Swedish chemist Jöns Jakob Berzelius (1779-1848).
catalysis ca·tal·y·sis (kə-tāl'ĭ-sĭs)
n. pl. ca·tal·y·ses (-sēz')
The action of a catalyst, especially an increase in the rate of a chemical reaction.