'anti-lactase' originates from Modern English, specifically combining the Greek-derived prefix 'anti-' and 'lactase' from Modern Latin/Neo-Latin 'lact-' + suffix '-ase', where 'anti-' meant 'against', 'lact-' meant 'milk', and '-ase' denoted 'enzyme'.

'lactase' was coined in biochemical terminology in the late 19th century from Modern Latin/Neo-Latin elements 'lact-' (from Latin 'lac', 'milk') and the enzyme-forming suffix '-ase'; later scientific usage combined the prefix 'anti-' with 'lactase' to form the compound 'anti-lactase' in modern English.

Initially, the components meant 'against' and 'milk enzyme' at the morphological level, but over time the compound came to specifically denote 'a substance that inhibits the enzyme lactase' in biochemical and medical contexts.