'autocollimator' originates from Greek and Latin roots: 'auto-' from Greek 'autos' meaning 'self', combined with 'collimator' (from Latin/French roots related to 'collimate', meaning 'to make parallel or direct into a straight line'), with the suffix '-or' indicating an instrument or agent.

'autocollimator' formed in modern technical English by combining the prefix 'auto-' (Greek 'autos') with 'collimator' (from French 'collimateur' and earlier Latin-derived forms) to denote an instrument that performs collimation or alignment automatically/self-referencing; the compound arose in the 20th century with developments in precision optics.

Initially coined to name an instrument that produces or checks collimation (making beams parallel), it came to be used more specifically for instruments that measure very small angular deviations by reflecting a beam from a mirror and comparing directions.