'predistributed' is formed from the prefix 'pre-' (from Latin 'prae-', meaning 'before') + 'distributed' (from Latin 'distribuere', meaning 'to divide, allot')

'distributed' comes from Latin 'distribuere' (dis- 'apart' + tribuere 'to assign'), which passed into Old French as 'distribuer' and Middle English as 'distributen'/'distribute'; the modern verb 'predistribute' is created by adding the Latin-derived prefix 'pre-' to mean 'distribute beforehand', yielding the participle 'predistributed'.

Initially, the Latin root meant 'to divide or assign apart'; over time 'distribute' came to mean 'to give out or allocate'. Adding 'pre-' shifted the combined meaning to 'to give out or allocate in advance', which is the current sense of 'predistributed'.