ironclad

adjective

1 sheathed in iron armor — used especially of naval vessels

2  so firm or secure as to be unbreakable: such as
2.1  binding (an ironclad contract)
2.2  having no obvious weakness

Merriam-Webster

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ORIGIN

The noun is an early name for 19th century warships built of wood but protected by steel or iron plates. The practice of fortifying ships in this way was first seen in the 1850s.

An ironclad was a steam-propelled warship protected by iron or steel armor plates used in the early part of the second half of the 19th century. The ironclad was developed as a result of the vulnerability of wooden warships to explosive or incendiary shells. The first ironclad battleship, Gloire, was launched by the French Navy in November 1859.

IRONCLADS were designed for several roles, including as high seas battleships, coastal defense ships, and long-range cruisers. The rapid development of warship design in the late 19th century transformed the IRONCLAD from a wooden-hulled vessel that carried sails to supplement its steam engines into the steel-built, turreted battleships and cruisers familiar in the 20th century.

This change was pushed forward by the development of heavier naval guns (the ironclads of the 1880s carried some of the heaviest guns ever mounted at sea at the time), more sophisticated steam engines, and advances in metallurgy which made steel shipbuilding possible.

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PRACTICE OWAD TODAY

Say something like:

"The company can't fire him, he has an IRONCLAD contract"