'ungrammatically' originates from the prefix 'un-' meaning 'not' and the word 'grammatical', which comes from the Greek word 'grammatikos', meaning 'pertaining to letters or learning'.

'grammatikos' transformed into the Latin word 'grammaticalis', and eventually became the modern English word 'grammatical'. The prefix 'un-' was added to form 'ungrammatical', and the adverbial form 'ungrammatically' was derived.

Initially, 'grammatikos' meant 'pertaining to letters', but over time it evolved into its current meaning of 'conforming to the rules of grammar'. 'Un-' negates this meaning.