ceticide (n.)

order of marine mammals containing 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.

word-forming element meaning "killer," from French -cide, from Latin -cida "cutter, killer, slayer," from -cidere, combining form of caedere "to strike down, chop, beat, hew, fell, slay," from Proto-Italic *kaid-o-, from PIE root *kae-id- "to strike." For Latin vowel change, see acquisition. The element also can represent "killing," from French -cide, from Latin -cidium "a cutting, a killing."