'fossil-fuel-related' is a modern compound combining 'fossil', 'fuel', and 'related'. 'fossil' originates from Latin, specifically the word 'fossilis', where 'fodere' meant 'to dig'. 'fuel' originates from Old French, ultimately from Latin 'focus', where 'focus' meant 'hearth'. 'related' originates from Latin, specifically the past participle 'relatus' of 'referre', where 're-' meant 'back' and 'ferre' meant 'to carry'.

'fossil' came into English via Medieval Latin 'fossilis' meaning 'dug up', becoming the modern English 'fossil'; 'fuel' passed from Old French into Middle English as forms like 'fuele' and evolved into modern 'fuel'; 'related' derived from Latin 'relatus' through Old French and Middle English verbs like 'relaten' and became the adjective 'related'.

Initially, the components meant 'dug up' (fossil), 'material for the hearth' (fuel), and 'brought back' or 'referred' (related); over time these meanings stabilized and the compound now specifically denotes things connected to fossil fuels or their impacts.