On the SitePoint PHP blog editor Bruno Skvorc has written up a post that talks about why a string is called a "string" going back through the history of the term and discovering its origins.

Why is a string called a string? Have you ever given this some thought? We never use such a word in contexts other than programming for a set of letters sticking together, and yet – in programming it’s as pervasive as the word “variable”. Why is that, and where does it come from?

To find out, we have to tackle some related terms first. History lesson time!

He starts with these related terms including "font", "uppercase" and "lowercase". He talks about the printing process and how the "stringing together" of the series of characters might have been how customers using the press were charged. He then shifts over to the academic world for background there relating to a series of numbers and letters used in decision problems. The term caught on and showed up in several other academic papers over the years ending up eventually in programming language definitions and examples.