Ordovician (adj.)

in reference to the geological period following the Cambrian and preceding the Silurian, 1879, coined by English geologist Charles Lapworth (1842-1920) from Latin Ordovices, name of an ancient British tribe in North Wales. The period was so called because rocks from it first were studied extensively in the region around Bala in North Wales. The tribe's name is Celtic, literally "those who fight with hammers," from Celtic base *ordo "hammer" + PIE root *weik- (3) "to fight, conquer." The geological period at first was considered as either part of the Silurian or the Cambrian, and Lapworth's proposed name took time to win universal acceptance, not receiving international approval as an official period until 1960.

Definitions of Ordovician

Ordovician (n.)
from 500 million to 425 million years ago; conodonts and ostracods and algae and seaweeds;
Synonyms: Ordovician period