The most common use of the word “argument” is to describe a disagreement. So the first time you hear “argument” to mean something you pass into a function (either a mathematical function or a programming language function), it sounds odd. How did “argument” come to mean two very different things? Here is an explanation.
It is curious to track the path by which the word “argument” came to have two different meanings, one in mathematics and the other in everyday English. According to the Oxford English Dictionary, the word derives from the Latin for “to make clear, prove”; thus it came to mean, by one thread of derivation, “the evidence offered as proof”, which is to say, “the information offered”, which led to its meaning in Lisp. But in the other thread of derivation, it came to mean “to assert in a manner against which others may make counter assertions”, which led to the meaning of the word as a disputation.
Taken from An Introduction to Programming in Emacs Lisp.
Update: As Dave Richeson points out in the comments below, there are really three meanings of “argument” being discussed.