The word terror originates from the Latin noun terror, meaning 'great fear, dread, alarm, panic'. This Latin noun is derived from the verb terrēre, 'to frighten, to terrify'. The core semantic thread from its ancient root to its modern usage is the concept of causing or experiencing intense, overwhelming fear. In English, it has evolved to denote both the profound emotional state itself and, by extension, the systematic use of violence to instill that fear, as seen in the term 'terrorism'.

Structure: terr (to frighten) + or (noun suffix) terr is from Latin terrēre, meaning 'to frighten, to terrify'. or is a Latin-derived noun-forming suffix indicating an agent or result.