The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
arg-
DEFINITION:
To shine; white; the shining or white metal, silver. Oldest form *2(e)r-, colored to *2(a)r-, becoming *ar- in satem languages and *arg- in centum languages. 1. Suffixed form *arg-ent-.argent, argentine, from Latin argentum, silver. 2. Suffixed form *arg-i-l(l)-.argil, from Greek argillos, white clay. 3. Suffixed form *arg-u-ro-.litharge, pyrargyrite, from Greek arguros, silver. 4. Suffixed form *arg-i-n-.arginine, from Greek arginoeis, brilliant, bright-shining. 5. Suffixed form *arg-u-, brilliant, clear. argue, from Latin denominative arguere, to make clear, demonstrate (< *argu-yo-). 6. Suffixed zero-grade form *g-ro-, becoming *arg-ro-.agrimony, possibly from Greek argos, white (< *argros). (Pokorny ar(e)-- 64.)