Literally "Good morning a fuck".
An ironic, vulgar salutation to answer to a "Good morning" sometimes used in Italy.
You can hear it mostly at work, early in the morning, from someone especially stressed out.
The intention of those using this expression is to warn their peers about a critical condition, a large workload to be processed soon or already in process, a really bad mood or all the above together.
Slang Jon Stewart often uses for the flu or common cold.
Based on the way he pronounces it (tongue-in-cheek Godfather character accent) it's probably the plural form of the Italian word 'bubbone,' a swollen lymph node characteristic of bubonic plague. It probably developed as slang for an infection because bubonic plague is so infectious. Stewart probably picked it up growing up in the NJ/NY area.
"I have the bubons again. It's the second time in three months. Let me say this to anybody out there with children at home: buy an autoclave."