'thoracic-related' is a compound formed from 'thoracic' + 'related'. 'Thoracic' ultimately originates from Greek 'θώραξ (thorax)', meaning 'breastplate, chest', adapted into Latin as 'thorax' and then into English as 'thoracic'.

'thoracic' came into English via Latin/Medieval Latin 'thorax, thoracicus' from Greek 'thorax (θώραξ)', and the modern compound 'thoracic-related' is formed in contemporary English by combining the adjective 'thoracic' with 'related' to indicate connection to the thorax.

Initially 'thorax' referred to a 'breastplate' or the chest area; over time it came to denote the anatomical chest region, and 'thoracic-related' now means 'having a relation to that chest region'.