Wellington vs Iron Duke

Wellington and Iron Duke both are nouns.

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

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

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

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

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