'high-pressure-related' is a compound formed from the adjective 'high', the noun 'pressure', and the past-participial adjective-forming element 'related'.

'high' originates from Old English 'hēah' meaning 'tall' or 'elevated'; 'pressure' comes via Old French/Modern French 'pression' from Late Latin 'pressura' (from Latin 'premere' meaning 'to press'); 'related' comes from Medieval Latin/Old French via Latin 'relatus', the past participle of 'referre' (to bring back, relate). These elements were combined in modern English to form the descriptive compound 'high-pressure-related'.

Initially, the components had separate senses ('high' = elevated, 'pressure' = pressing force, 'related' = connected). Over time they were combined in modern usage to denote things that are connected with or caused by elevated pressure; the compound expresses a direct relation to 'high pressure' rather than separate, unrelated notions.