'asternia' originates from Neo-Latin, specifically the word 'asternia', where the prefix 'a-' meant 'without' and 'sternum' (from Latin) meant 'breastbone'.

'asternia' was formed in medical/Neo-Latin by combining the privative prefix 'a-' with Latin 'sternum' (from Greek 'sternon', meaning 'chest'), and was adopted into English medical usage from medical Latin.

Initially it meant 'absence of the breastbone' in medical Latin, and this core meaning has remained essentially unchanged in English medical usage.