Part of speech: Noun
Plural forms: kellies, kellys
In slang use, kelly refers to a man’s stiff hat, such as a derby or a straw skimmer.
Kelly /ˈkɛlɪ/ — a personal name used as both a first name and a surname.
Example:
Gene Kelly — full name Eugene Curran Kelly — was a celebrated American dancer, actor, and choreographer known for his dynamic performances in classic Hollywood musicals.
Author’s summary: The term kelly can describe a type of stiff hat in slang, while as a proper noun it functions as a personal or family name, notably linked to Gene Kelly.