'pre-date' (sense 'occur earlier') is formed in modern English from the prefix 'pre-' (from Latin 'prae-' meaning 'before') plus 'date' (from Latin 'datum' meaning 'given' or 'a point in time'). Separately, the 'predate' that means 'to prey on' is historically related to Latin 'praedari' (to plunder) / 'praeda' (booty).

'pre-date' (occur earlier) is a relatively transparent modern compound of 'pre-' + 'date' in English. The 'prey' sense derives ultimately from Latin 'praedari' > Late Latin/Old French forms around 'praeda'/'predare', which entered English lexical history as words related to 'predation' and then produced the verbal sense 'predate' in modern usage.

Initially the components meant 'pre-' = 'before' and 'date' = 'a point in time', giving the straightforward sense 'to come before in time'. The other sense comes from Latin 'praedari' meaning 'to plunder' and developed into the biological sense 'to prey on'; both senses coexist in modern English under the form 'predate'.