Merriam-Webster's first definition for "argument" is the obsolete "indication". Perhaps that's where argument derived its meaning in math, physics, and other sciences.
Jeff japhy Pinyan,
P.L., P.M., P.O.D, X.S.:
Perl,
regex,
and perlhacker How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart