'anagrammatically' originates from English, specifically from the word 'anagrammatical' with the adverbial suffix '-ly', where 'anagrammatical' is derived from 'anagram'.

'anagrammatical' comes from 'anagram', which itself comes from the Greek word 'anagrammatismos', and eventually became the modern English word 'anagrammatically' with the addition of '-ly'.

Initially, it meant 'in a way relating to anagrams', and this meaning has remained the same in modern usage.