infusorial earth
noun
in·fu·so·ri·al earth ˈin-fyü-ˈzȯr-ē-əl- 
-ˈsȯr-
: kieselguhr
Word History
Etymology
infusorial "relating to or containing infusorians," from New Latin Infusoria "group of minute organisms found in infusions of decaying matter" + -al entry 1 — more at infusorian
First Known Use
1868, in the meaning defined above