"pertaining to the whale," 1640s, from Latin cetus (see Cetacea) + -aceous.
Entries linking to cetaceous
Cetacea n.
order of marine mammals including whales, 1795, Modern Latin, from Latin cetus "any large sea creature" (whales, seals, dolphins), from Greek kētos "a whale, a sea monster," which is of unknown origin, + -acea.
-aceous
word-forming element denoting "belonging to, of the nature of," from Latin -aceus, enlarged form of adjectival suffix -ax (genitive -acis); see -acea. Especially in biology, "pertaining to X order of plants or animals."