canon

ˈkænən

A general rule, law, or principle; an accepted collection of sacred books; a member of a cathedral chapter.

canonicus
"according to rule", in Latin (Indo-European), Classical Period, Roman Empire
kanna
"reed", in Ancient Greek (Indo-European), Classical Period, Greece
kanōn
"measuring rod, standard", in Ancient Greek (Indo-European), Classical Period, Greece

Religious canons, civil laws are cruel

Shakespeare, Timon of Athens, Act 4, Scene 3

Historical

canon /canon/

Classical Latin, Roman Empire

κανών /kanōn/

Classical Greek, Greece