deleterious

The word 'deleterious' has a direct lineage from ancient Greek, entering English via scientific Latin. Its core component, 'deleter,' originates from the Greek dēlētēr, meaning "a destroyer," which itself derives from the verb dēleisthai ("to hurt, to damage"). This root carries the fundamental sense of causing ruin or harm. In the 17th century, the word was adopted into English in its adjectival form, primarily used in scientific contexts to describe subtly poisonous or injurious agents. Over time, its usage broadened to describe anything that has a harmful and often hidden damaging effect, perfectly preserving the destructive essence of its ancient Greek root while applying it to abstract concepts like influence or policies.

Structure: deleter (destroyer) + ious (adjective suffix) deleter (from Greek dēlētēr, meaning "destroyer," from the verb dēleisthai, "to hurt, to damage") + ious (English adjective-forming suffix, from Latin -iosus, meaning "full of, characterized by").