'antimysticalness' originates from Modern English, formed by the prefix 'anti-' (from Greek 'anti' meaning 'against') + the adjective 'mystical' (from Late Latin 'mysticus' and Greek 'mustikos' meaning 'mystical, secret') and the nominalizing suffix '-ness'.

'antimysticalness' was created in Modern English by combining 'anti-' + 'mystical' + '-ness'. The element 'mystical' derives from Late Latin 'mysticus' and Greek 'mustikos', while 'anti-' comes from Greek 'anti-' and '-ness' is an Old English/Old Germanic nominalizing suffix.

Initially the components literally meant 'against' + 'mystical/secret', and over time the combined term has been used to denote a general opposition to mysticism or mystical explanations.