'antipudic' is formed in English from the prefix 'anti-' (from Greek/Latin meaning 'against') combined with 'pudic' from Latin 'pudicus', where the root 'pud-' (from Latin 'pudere') meant 'to be ashamed'.

'pudic' comes from Latin 'pudicus' (meaning 'chaste, modest'), which entered English via Late/Medieval Latin and Middle English; 'antipudic' arose by affixing 'anti-' to 'pudic' to express opposition to modesty.

Originally the Latin root related to shame or modesty; over time the formed English adjective 'antipudic' came to mean 'against or lacking modesty', i.e. 'insensible to shame' in modern usage.