I have never thought about until recently, but I'm not sure why we call strings strings. I am a .NET programmer, but I believe the concept of strings exist in virtually every programming language.
Outside of programming, I don't believe I've heard the word string used to describe words or letters. A quick Google of, 'Define: string' yields a bunch of definitions that have nothing to do with the concept of letters, words, or anything of the nature associated to programming.
My guess of it, is that, back in the day, strings were really just arrays of characters of a particular length, often with a delimiting character at the end. But, I don't see a natural transition from 'character array' to string.
Can someone offer up some insight to why we call strings strings?
From this reference:
The 1971 OED (p. 3097) quotes an 1891 Century Dictionary on a source in the Milwaukee Sentinel of 11 Jan. 1898 (section 3, p. 1) to the effect that this is a compositor's term. Printers would paste up the text that they had generated in a long strip of characters. (Presumably, they were paid by the foot, not by the word!) The quote says that it was not unusual for compositors to create more than 1500 (characters?) per hour.