What does tessio mean?

"Tessio" is not a word with a common, established meaning. It's likely you're referring to "Tessio" from The Godfather movie and book series.

In the story, "Tessio" is a caporegime (captain) in the Corleone crime family. He's a trusted lieutenant of Don Vito Corleone and is initially loyal to the family.

Therefore, "Tessio" in this context refers to a specific fictional character, not a word with a broader meaning.