'unspiritually' originates from the prefix 'un-' (Old English 'un-') attached to the adjective 'spiritual' and the adverbial suffix '-ly'; 'spiritual' in turn comes via Middle English from Old French and Latin origins.

'spiritual' comes from Latin 'spiritus' meaning 'breath, spirit', passed into Old French as 'spirituel' and Middle English as 'spiritual'; the negative prefix 'un-' was added in Modern English to form 'unspiritual', and then the suffix '-ly' produced the adverb 'unspiritually'.

Initially 'spiritual' referred to matters of the spirit or breath (Latin 'spiritus'); over time the word came to mean 'relating to religion or the non-material mind', and 'unspiritually' now denotes the absence of those qualities or attitudes.