Lateral spent most of its English life as a technical term that few people outside medicine or engineering had reason to use. It derives from Latin latus ('side'), through the adjective lateralis ('belonging to the side'), and entered English in the 15th century for anatomical descriptions — the lateral ventricles of the brain, lateral muscles, lateral movements. Roman military writers used latus for the flanks of army formations, where attacks were most dangerous, giving the word an early association with vulnerability and strategic positioning. The family it belongs to is revealing. Bilateral means 'two-sided', unilateral means 'one-sided', collateral means 'side by side', and equilateral means 'equal-sided'. All derive from the same Latin root, and together they cover an impressive range of legal, geometric, and diplomatic concepts. The word's transformation came in 1967, when Maltese-born psychologist Edward de Bono published 'The Use of Lateral Thinking'. His metaphor was simple but effective: conventional thinking attacks problems directly, while lateral thinking approaches from the side. The phrase caught fire. Within a decade, lateral thinking had entered common usage, and lateral itself had shed its purely anatomical associations for good.