I am familiar with the phrase "translator, traitor" and have no issue with its meaning in English. But what is the pun referred to on this Wikipedia page:
"Similarly, consider the Italian adage "traduttore, traditore": a literal translation is "translator, traitor". The pun is lost, though the meaning persists. (A similar solution can be given, however, in Hungarian, by saying a fordítás: ferdítés, which roughly translates as "translation is distortion".)"