'tighten' originates from the English adjective 'tight' plus the verb-forming suffix '-en', where 'tight' meant 'close or firm' and '-en' formed verbs meaning 'make or become'.

'tighten' developed in Middle English from forms such as 'tigten' or 'tighten' formed by adding '-en' to 'tight'; 'tight' itself comes from Old English and earlier Germanic roots meaning 'compressed' or 'close'. Over time the compound became the modern verb 'tighten'.

Initially, it meant 'to make close or firm', and over time its use broadened to include making regulations stricter and figurative senses like 'to make tense'; the core idea of making something less loose has remained.