The operative phrase there is "considered to have entered the language as an everyday word". The acronym "PIN" has morphed into the term "pin number" meaning "A

The operative phrase there is "considered to have entered the language as an everyday word". The acronym "PIN" has morphed into the term "pin number" meaning "A personally-identifying number usually associated with financial transactions". Yes, it's redundant, but the point is that it's not being used as an acronym, but as a separate part of the lexicon with its own meaning.