Note for example (in British English) Wellingtons (and wellies) meaning rubber boots, from Duke of Wellington. The reverse process is usually historical and is mainly found in family names, such as Smith, Cooper, Bell, etc. As for why this happens, it is generally impossible to give an answer for the history of language.
A common noun is a word for any person, place, or thing.
A proper noun is the name of a person, place, or thing.
Examples:
common noun: proper noun
apple: Apple iPad
buffalo: Buffalo, NY
hope: The Hope Diamond
stone: Sharon Stone, actress
war: War and Peace by Leo Tolstoy
They are important because they are different parts of speech.
A common noun is a word for any person, place, thing, or idea. A common noun is capitalized only when it is the first word in a sentence. Examples:
parent
country
cabbage
peace
A proper noun is the name of a specific person, place, thing, or a title. A proper noun is always capitalized. Examples:
Atticus Finch
Eiffel Tower
War and Peace by Leo Tolstoy
"Park Avenue" is a proper noun, because it is a place. Proper nouns like this should always be capitalized.
Revolution is a common noun. If a common noun is part of a name, it becomes a proper noun. Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things. Pronouns can usually replace proper and common nouns.
Robin is a proper noun when it is a name, but common when it is the bird. Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things. If a common noun is part of a name, it becomes a proper noun. Pronouns always replace proper and common nouns.
Olympic is a Proper noun. Proper nouns are the unique names of people, places, or things. Common nouns are words for general things. Pronouns replace proper and common nouns.
Development is a common noun. Proper nouns are the unique names of people, places, or things. Common nouns are words for general things. Pronouns replace proper and common nouns.
probaly there is a name, ex: frank, and someone elses name is frank, then that is a common and proper noun
A proper noun is the name of a specific person, place, or thing. Common nouns may be capitalized only at the beginning of a sentence, but that does not make them proper nouns, it just makes them capitalized common nouns.
Proper nouns are specific names given to unique persons, places, or things, starting with a capital letter. They distinguish from common nouns by pointing to a particular entity, for example, "New York City" instead of just "city." Proper nouns are used to identify individual entities and convey specificity in communication.
Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things. Pronouns always replace proper and common nouns.
"Park Avenue" is a proper noun, because it is a place. Proper nouns like this should always be capitalized.
Revolution is a common noun. If a common noun is part of a name, it becomes a proper noun. Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things. Pronouns can usually replace proper and common nouns.
Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things. Pronouns can usually replace proper and common nouns.
common
Proper noun
Proper nouns are the unique names of people, places, or things. Common nouns are the words for general things.
You can sometimes us a proper noun in place of a common noun but you would have to change the sentence. You should use a pronoun instead.
Proper Nouns: Used to define the specific name of a noun. Common Nouns: The general form of nouns.