'antacid' originates from a combination of Greek and Latin elements: the Greek prefix 'anti' (from Greek 'anti') meaning 'against' and the Latin word 'acidus' meaning 'sour' (acid).

'antacid' was formed in English in the 19th century by combining the prefix 'anti-' with 'acid' and came into use as the modern English word 'antacid'.

Initially it literally meant 'against acid' (i.e., opposing acid); over time it came to refer specifically to substances that neutralize stomach acid and relieve related symptoms.