'deglorify' is formed in English from the prefix 'de-' plus the verb 'glorify'; 'de-' comes from Latin 'de-' meaning 'off, away, down', and 'glorify' comes from Latin 'glorificare' where 'gloria' meant 'glory' and 'ficare' (from 'facere') meant 'to make'.

'glorificare' (Latin) passed into Old French as 'glorifier' and into Middle/Modern English as 'glorify'; the compound 'deglorify' was later formed in English by adding the prefix 'de-' to 'glorify' to express reversal or removal.

Originally the elements meant 'to make glorious' (glorify) and the prefix 'de-' meant 'remove/oppose'; over time 'deglorify' came to mean 'to remove or reduce glory, praise, or reverence' in modern usage.