'bi-fold' is a compound formed from the prefix 'bi-' and the verb/noun 'fold'. The prefix 'bi-' comes from Latin 'bis' meaning 'twice', and 'fold' comes from Old English 'fealdan' meaning 'to fold.'

'fold' originates from Old English 'fealdan' and evolved into Middle English 'folden' and the modern English 'fold'; 'bi-' as a combining form from Latin 'bis' has been used in English compounds since the medieval period. The compound 'bi-fold' (also written 'bifold') arose in modern English to describe something folded in two, especially printed materials.

The elements originally meant 'twice' and 'to fold'; over time the compound came to specifically denote 'folded in two' and, by extension, objects (such as brochures or wallets) designed with a single fold into two panels.