'past-related' is a modern English compound formed from the adjective 'past' and the past-participle adjective 'related' (from 'relate'). 'Past' comes from older Germanic/Old English roots meaning 'that which has passed', and 'related' ultimately traces to Latin 'relatus' (via the verb 'relate').

'past-related' developed in Late Modern English by combining 'past' (an Old English-derived adjective) with 'related' (the past participle/adjectival form of 'relate', which entered English via Old French/Latin influence). The compound reflects a straightforward combination rather than a long separate historical form.

The compound originally and consistently meant 'connected to what has gone by' or 'concerning the past'; its basic meaning has remained stable as a descriptive phrase for things pertaining to past events or conditions.