I quite enjoy questions about Unix history.
They provide a nice way of learning how something came about, and will in the end (if the answer is good) give me a better understanding of the evolution of the tools at the centre of one of my main professional hobbies.
It's a pity that this particular question hasn't been reopened, and that it has, so far, only gathered (IMHO) mediocre answers (from a history point of view)1. Yes, it's GNU Readline rather than Bash that uses Ctrl+T to transpose characters, but where did that come from? Well, it's from Emacs, and it was present in Emacs 18 (ref to
lisp/simple.el in the source distribution, from 1992). Can we say anything about older versions of Emacs with regards to this? Influences from other editors (TECO, for example)? And so on... ideally ending up with names of actual human beings making decisions on particular dates (or at least in or around some year). It makes it relatable.
1 Except for Stephen Kitt's answer in a comment to the question.