Um, first of all, “I’m So Tired” precedes “Blackbird” on the album. The song right before it is “Martha My Dear.”
Second, in the Gospel According to Lewisohn and other sources, that snippet is John speaking forwards, mumbling, “Monsieur, monsieur, may I have another one?” like a drunk. Sort of fits in with the theme of “I’m So Tired.”
You know, it might be sick, but every time hear about the whole “Paul is Dead” schtick some evil part of my mind says "Yeah, but they’re doing a much better job with the “John is Dead” schtick.