The word 'deums' is not in the Latin language. The correct word is 'deos', which acts as the direct object of the verb, and therefore is in the accusative case. The equivalent meaning in English is the word gods. The singular form of the word is 'deum', which is used most famously in the ancient liturgical hymn 'Te Deum Laudamus', which means 'We praise thee, God'. And so the phrase has been passed down in English about getting done one's 'te deums', or praises to God.
God (accusative singular).