'tricyclic' originates from a modern English compound formed from the prefix 'tri-' (from Greek 'trís') and 'cyclic' (from Greek 'kyklos'), where 'tri-' meant 'three' and 'kyklos' meant 'circle' or 'ring'.

'tricyclic' is a 20th-century English formation combining 'tri-' and 'cyclic'; 'cyclic' itself came into English via Latin/Medieval Latin 'cyclus' (from Greek 'kyklos') and related French/Latin forms before stabilizing in modern English usage.

Initially, the elements conveyed the literal sense of 'having three cycles or rings'; over time the compound came to be used in chemistry for three-ring molecular structures and, from the mid-20th century, specifically in medicine to name a class of antidepressant drugs ('tricyclic antidepressants').