cretaceous (adj.)youdaoicibaDictYouDict[cretaceous 词源字典]
1670s, "chalky," from Latin cretaceus "chalk-like," from creta "chalk." As a geological period (with a capital C-), it was first used 1832. The extensive chalk beds of southeastern England were laid down during the Cretaceous.[cretaceous etymology, cretaceous origin, 英语词源]