'retrosternal' originates from Latin elements, specifically the prefix 'retro-' (Latin) meaning 'back' or 'behind' and 'sternum' (Latin) meaning 'breastbone', with the adjective-forming suffix '-al'.

'retrosternal' developed as a Neo-Latin/medical English compound from Latin 'retro-' + Latin 'sternum' (and adjective form 'sternalis') and entered modern medical English usage in the late 19th to early 20th century.

Initially, it meant 'located behind the sternum', and this core meaning has remained stable into current medical usage as 'situated or occurring behind the breastbone'.