'prepartition' originates from Latin and Old French elements: the prefix 'pre-' from Latin 'prae' meaning 'before', combined with 'partition' from Latin 'partitio' (from 'partire'/'partire' meaning 'to divide').

'partition' came into English via Old French from Latin 'partitio'; the prefix 'pre-' (from Latin 'prae') was attached in Modern English to form 'prepartition', and the past-participle/adjective form 'prepartitioned' developed by regular verbal inflection.

Initially related to the general idea of 'division' ('partitio' = division), combined with 'pre-' it came to mean 'division done before (an event)', and now denotes 'divided in advance' or the action of having divided in advance.