'anti-proton' originates from the combination of the prefix 'anti-' (from Greek 'anti-' meaning 'against' or 'opposite') and the word 'proton' (from Greek 'protos' meaning 'first').

'anti-proton' was formed after the coining of 'proton' (coined in the early 20th century) by adding the scientific prefix 'anti-' to denote the antiparticle; the antiproton itself was discovered and named following experimental verification in 1955 by Emilio Segrè and Owen Chamberlain.

Initially, 'proton' derived from a root meaning 'first,' but over time it became the technical name for the subatomic particle; 'anti-proton' developed later to denote the particle opposite in charge to the proton.