Either measuring instruments marked with linear units, or people who exercise supreme authority over a country or territory.
From Old French riule, from Latin regula meaning 'straight stick, rule, pattern'. The tool meaning came first (13th century), referring to a straight edge for measurement. The 'sovereign' meaning developed in the 14th century through the metaphor of keeping things 'in line' or under control.
The dual meaning of 'ruler' - both measuring stick and sovereign leader - reflects the ancient metaphor of governance as bringing order and straight lines to chaos. This linguistic parallel suggests that humans have long understood leadership as fundamentally about establishing standards and maintaining proper proportions in society.
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