infanticide comes from Late Latin infanticidium ('killing of an infant'), from Latin infans ('infant') + -cidium ('a killing'), from caedere ('to cut, kill'). Morphologically, the ending is part of the etymology: the suffix is attached to the older base named in the history, producing a later English derivative. In present English, the noun sense is "the killing of an infant, or a person who commits it", so the historical development ends in a clearly identifiable modern dictionary use. The same base also appears in related forms such as infant, infantile, homicide, and genocide, and in derivatives such as infanticidal. Its semantic neighborhood includes child-murder, which helps locate the modern sense without adding a separate etymological claim. The named historical forms include Latin infans and Latin caedere.