'levothyroxine' originates from modern scientific/chemical naming, combining the prefix 'levo-' (from Latin 'laevus', meaning 'left', indicating the levorotatory isomer) and 'thyroxine' (the name of the thyroid hormone).

'thyroxine' developed as a name from 'thyroid' (from Greek 'thyreoeides', meaning 'shield-like') with the chemical/amine suffix '-ine'; in the 20th century the specific term 'levothyroxine' was coined in medical chemistry to denote the levorotatory form of thyroxine used pharmaceutically.

Initially the elements named the chemical structure/form of the hormone; over time 'levothyroxine' became used primarily to refer to the manufactured drug preparation used to replace or supplement natural T4 in clinical treatment.