'preinitial' originates from Modern English, formed by combining the prefix 'pre-' (from Latin 'prae', meaning 'before') with the adjective 'initial' (from Latin 'initialis'/'initium', meaning 'beginning').

'initial' derives from Latin 'initium' (via medieval/Old French and Middle English forms 'initial'), and the compound 'preinitial' was created in Modern English by prefixing 'pre-' to 'initial'.

Initially it meant 'before the initial (stage or point)', and this literal sense has remained largely unchanged in modern usage.