'antirachitical' originates from New Latin, specifically the word 'antirachiticus', where 'anti-' meant 'against' and 'rachit-' (from Greek 'rhakhis') related to 'spine' or the disease rachitis (rickets).

'antirachitical' changed from Late Latin/New Latin 'antirachiticus' and through Modern Latin and early medical English forms such as 'antirachitic' it eventually became the English adjective 'antirachitical'.

Initially, it meant 'against rachitis (rickets)', and over time it has retained that medical sense of 'preventing or treating rickets'.