As I was chatting with some friends, the subject of my recent knowledge of Unary, Binary and Trinary operators that had read from the Camel popped up. I was instantly corrected for using Trinary with Ternary. I was momentarily a-taken back that I had made such a mistake, when I had only just read about it. But the two people to whom I was chatting have a more vast knowledge of computer science that I conceded to the correction, until I check the book again. At which point they still did not believe that Trinary was the term that was used in the book. Only after I had offered to take a photo of the pages did they relent that this wasn't some sort of joke.

These friends, each knowing their fair share of languages (Java, C, C++, Cobol plus many more) with one being very proficient in Perl, said they had never heard of the term Trinary and that it must be some sort of made up word. And the fact that it was used when Ternary already existed and both seemingly having the exact same meaning, when used to describe an operator in a programming language. Their lack of knowledge pertaining to existence of the term Trinary and their utter disregard to accept it as a real term, even a real English word, surprises me.

So what I would like to know is:

1. Is there a difference between Trinary, Ternary (in operator specific context).
2. Why is Trinary used primarily in the Camel.
3. How could two very knowledgeable people not know of such a term.
4. Possibly some background history on the terms themselves.