ordinance

In Anglo-Norman French, ordinance meant 'arrangement' or 'decree,' from Latin ordinare, 'to put in order.' When medieval English governments issued decrees about military supplies — cannons, ammunition, siege equipment — the documents were called ordinances. The weapons themselves began to be called 'the ordnance' as a shorthand for 'the stuff described in the ordinance.'

By the 1500s, the spelling had split. 'Ordinance' kept its legal meaning — a municipal law, a decree. 'Ordnance' dropped the 'i' and became exclusively military — weapons, ammunition, artillery. The Board of Ordnance, established under Henry VIII, managed the Crown's weapons and fortifications. The separation was complete: one word for law, one word for guns.

The Ordnance Survey, Britain's national mapping agency, was founded in 1791 to map Scotland after the Jacobite rising. The military origin is right in the name — these were maps made by the Board of Ordnance for military purposes. The world's most beloved hiking maps began as tools for suppressing rebellion.

English now treats ordnance and ordinance as completely separate words, though they are etymological twins. Ordnance means military weapons and ammunition. The U.S. Army Ordnance Corps manages weapons systems. EOD (Explosive Ordnance Disposal) teams handle bombs. A single dropped letter in the 1500s created a permanent lexical split. The bureaucratic decree and the cannon it authorized went their separate ways.