Iron Duke vs Wellington

Iron Duke and Wellington both are nouns.

Word	Noun	Adjective	Verb	Adverb
Iron Duke	Yes	No	No	No
Wellington	Yes	No	No	No

As nouns, Iron Duke and Wellington are synonyms defined as:

Iron Duke and Wellington: British general and statesman; he defeated Napoleon at Waterloo; subsequently served as Prime Minister (1769-1852)

Other synonyms of Iron Duke include Arthur Wellesley, Duke of Wellington, First Duke of Wellington.

Iron Duke (noun)	Wellington (noun)
British general and statesman; he defeated Napoleon at Waterloo; subsequently served as Prime Minister (1769-1852)	(19th century) a man's high tasseled boot
	the capital of New Zealand
	British general and statesman; he defeated Napoleon at Waterloo; subsequently served as Prime Minister (1769-1852)