'tach' originates from English, specifically the word 'tachometer', where 'tach-' ultimately derives from Greek 'tachys' meaning 'swift' and '-meter' from Greek 'metron' meaning 'measure'.

'tach' developed as a clipped/informal form of 'tachometer' (coined in the 19th century from Greek elements) and was adopted into colloquial and technical speech as a short label for the instrument; later it also appeared as shorthand in clinical notes for 'tachycardia'.

Initially, it meant the shortened name for the instrument 'tachometer'; over time it retained that sense but also expanded into medical shorthand for a fast heart rate and occasional informal verb usage meaning 'to check with a tachometer'.