'anti-neutron' originates from a combination of the prefix 'anti-' and the word 'neutron'. 'anti-' originates from Greek, specifically the word 'ἀντί' (anti), where 'anti-' meant 'against' or 'opposite', and 'neutron' comes via New Latin from Latin 'neuter' (from Greek roots) meaning 'neither' or 'neutral'.

'anti-neutron' was formed by adding the prefix 'anti-' to the modern scientific term 'neutron'. The term 'neutron' was coined in the early 20th century to name the neutral subatomic particle discovered experimentally in 1932; 'antineutron' arose in mid-20th-century particle-physics literature to denote the neutron's antiparticle.

Initially, the elements 'anti-' and 'neutron' separately meant 'opposite/against' and 'neutral particle' respectively; when combined they retained the straightforward modern meaning 'the particle opposite to the neutron (the neutron's antiparticle)'.