'proton' originates from Greek, specifically the word 'prōtṓn', where 'prōt-' meant 'first'.

'proton' changed from Greek 'prōtṓn' into New/Modern Latin 'proton' and was adopted into English scientific usage in the late 19th to early 20th century (coined as the name for the hydrogen nucleus).

Initially, it meant 'first' or 'primary' in Greek, but over time it evolved into the modern scientific meaning 'a positively charged subatomic particle' (and, in chemistry, 'a hydrogen ion').