They told me I was gullible … and I believed them

A number of years ago a friend told me a joke that I have never been able to work out. He told me that the word gullible was not in the dictionary.

Well I went and looked it up, and it was in the dictionary. So I went back to my friend, and I said “Hey, you said that the word gullible is not in the dictionary, but it is”. My friend then told me that I had misheard him and that the word gullible was in the dictionary, but because it is not actually an English word it was not in the Oxford English dictionary.

Well I went and looked up the Oxford English dictionary and it was there as well. So I went back to my friend and I said “Hey, you said that the word gullible was not in the Oxford English dictionary, but it is”. My friend then told me that I had misheard him and that it was in the dictionary and that it was an English word but because of complications with the word origin they had to change the spelling of the word gullible.

Well I went and looked up the dictionary again and the spelling hadn’t changed at all. So I went back to my friend, and I said “Hey, you said that they had changed the spelling of the word gullible, but they haven’t”. My friend then told me that I had misheard him, and that it was in the dictionary, it was an English word and it was the same spelling, but they were thinking of taking it out of the dictionary sometime soon.

Well I have been checking the dictionary ever since, including each and every new dictionary I see or buy, and it is still there, the same word, the same spelling. I have never found any of this funny, but my friend laughs every time it is mentioned. Can anyone explain the joke to me?