the.com/rule
A line drawn by someone hoping you'll forget they drew it.
means A stated principle or instruction that governs conduct, procedure, or what counts as correct — or, as a verb, to exercise authority over something.
from From Latin 'regula,' a straight stick or ruler, the carpenter's tool for keeping a line true — itself from 'regere,' to lead straight or direct (a cousin of 'regent,' 'regular,' and 'regime'). It traveled through Old French 'reule' into English, so the very word carries the image of a straightedge: a rule is literally something laid down to keep you from wandering off the line.
latin rootRegula meant a straight stick for measuring
of thumbLikely from brewers gauging beer heat by touch
golden oneAppears in nearly every major religion independently
the exceptionProving rules is a mistranslation of testing them