What's the "een" in Halloween?
transposition of letters in a word so as to form another, 1580s, from French anagramme or Modern Latin anagramma (16c.), both from Greek anagrammatizein "transpose letters," from ana- "up, back" (see ana-) + gramma (genitive grammatos) "letter" (see grammar). Related: Anagrammatical; anagrammatically.
the transposing of the letters of a word or group of words to produce other words that possess meaning, preferably bearing some logical relation to the original. The construction of anagrams is of great antiquity. Their invention is often ascribed without authority to the Jews, probably because the later Hebrew writers, particularly the Kabbalists, were fond of them, asserting that "secret mysteries are woven in the numbers of letters." Anagrams were known to the Greeks and Romans, although known Latin examples of words of more than one syllable are nearly all imperfect. They were popular throughout Europe during the Middle Ages and later, particularly in France, where a certain Thomas Billon was appointed "anagrammatist to the king."