5. Klick
A klick isn’t actually an unusual measurement – it’s just military slang for kilometre. It is said that the term derives from a form of measurement conducted during military treks, in which designated soldiers would count the paces of the troops, moving the gas regulator on their rifles back by one mark every 100 metres. After ten marks they would reset the regulator – indicating 1,000 metres – which would make a ‘click’ sound.