"Explanation: It's just that... you have all these squishy parts, master. And all that water! How the constant sloshing doesn't drive you mad, I have no idea."
Meatbag was a slang term sometimes used by droids to refer to organics. The term was generally considered offensive by most organics, and it was normally used as a means to insult them.
The term originated with the character HK-47 from Star Wars: Knights of the Old Republic, who was the first and most well-known user of the word in the Star Wars universe. His usage of the term is a possible reference to the character Bender from Futurama, who would also often refer to Humans as "meatbags."[source?]
In the RPG Sonic Chronicles: The Dark Brotherhood, the robot character E-123 Omega refers to the other characters as "meatbags", most likely as a nod to the original use by HK-47, especially considering that the same developer produced Star Wars: Knights of the Old Republic.