'retro-sternal' originates from a modern medical/Latin formation combining the Latin prefix 'retro-' and the Latin noun 'sternum'; 'retro-' comes from Latin 'retro' meaning 'back' or 'behind', and 'sternum' comes via Latin from Greek 'stérnon' meaning 'breastbone'.

'stérnon' (Greek) became Latin 'sternum', which gave rise to the adjective 'sternal' in later Latin/English medical usage; the Latin prefix 'retro-' has long been used in New Latin and medical compounds to mean 'behind', and these elements were joined in modern English to form 'retro-sternal' (also seen as 'retrosternal').

Initially the component parts meant 'behind' (retro-) and 'breastbone' (sternum); the combined term has kept this literal anatomical meaning and is used in medicine to describe location or symptoms behind the sternum.