early 17th cent.: from Latin planum 'flat surface', neuter of the adjective planus 'plain'. The adjective was suggested by French plan(e) 'flat'. The word was introduced to differentiate the geometrical senses, previously expressed by plain, from the latter's other meaningsearly 20th cent.: shortened formMiddle English: from a variant of obsolete French plaine 'planing instrument', from late Latin plana (in the same sense), from Latin planare 'make level', from planus 'plain, level'late Middle English: from Old French, from Latin platanus, from Greek platanos, from platus 'broad'