Why is it wrong to say "My names are"?

I know this much: Your first and last names are considered a collective noun. But I don't know why that is.

One site defines collective nouns like this:

Collective nouns are names for a collection or a number of people or things. Words like group, herd, and array are collective noun examples.

So, my question is, shouldn't this mean that a collective noun is one name for many things instead of many names for one thing? If it does have this sense, then your first and last names isn't a collective noun, is it?

Or is there another explanation for villainizing the introduction "My names are..."?

Solution 1:

I know so much: Your first and last names are considered a collective noun. But I don't know why that is.

First and last names together do not make a collective noun; they make a compound noun.

A noun is the name of a person, place, or thing. When a name, whether it is a person, building, or organization, or something else, points to a particular person, building, etc., it is called a proper noun. Some proper nouns are only one word: Mike, Albert, Snickers, Pepsi, etc. Sometimes two word or more words can be joined together to form a compound noun. There are rules for how they are joined together, which is another topic, but here are several compound nouns (remember they act together to make ONE noun): prizefighter, beach ball, newsstand, news room, sister-in-law.

When a compound noun is a proper noun, it too is still considered one noun, even if it spans multiple words.

John Smith

John is in his office.

Mr. Smith is not in his office today.

John Smith is back in his office.

Mexico City is in Mexico. The Metropolitan Opera House is in New York. We have terrible news; the George Washington Elementary School has lost its credentials and will be closed down by the city.

Sometimes a person will go by an 'alias' which is like a fake name, a substitute name, used instead of the person's real name.

: otherwise known as --Webster's. alias. adv.

So, here you can use "are." My names are Wilbert Brown, Martin Thomas, and Andrew Welch. My real name is Wilbert Brown. Martin Thomas is my "pen" name I use in writing fiction novels, and Andrew Welch is a business name I use occasionally.

This is a real good explanation of how 'collective' nouns can be singular or plural:

http://www.chompchomp.com/terms/collectivenoun.htm

Compound noun:

https://www.englishgrammar101.com/module-1/nouns/lesson-6/compound-nouns

Solution 2:

There is no convention for saying My names are John Smith.

Why that is, I have no idea - the reasons are lost in the mists of time.But it would be quite non-idiomatic.

However, if you have both a name and a nom de plume, you could say My names are Eric Blair and George Orwell.

If someone tells you they are John Smith, and you need any further middle names they may have, you could say any one of the following:

Is that your full name? Do you have a middle name? Do you have any other Christian names.

Solution 3:

For the vast majority, a full name consists of two or more parts. A person's identity is not limited to their first name ( the secular version of christian name), when filling out official forms we also include any middle names we might have, and then our last name (also called surname or family name)

When someone asks: "What is your name?" they are usually referring to our first name, e.g. John; otherwise, they will ask: "What's your full name?"

The conventional reply is: "It's John Malcolm Smith". Sometimes, people have a double surname, also called a double-barreled name,a combination of their mother and father's last names: e.g. John Malcolm Fitzgerald-Smith.

I found a Wikipedia article which sums up nicely the situation.

A personal name or full name refers to the set of names by which an individual is known and that can be recited as a word-group, with the understanding that, taken together, they all relate to that one individual. (...)
In Western culture, nearly all individuals possess at least one given name (also known as a personal name, first name, forename, or Christian name), together with a surname (also known as a family name, last name, or gentile name)—respectively, the Thomas and Jefferson in Thomas Jefferson—the latter to indicate that the individual belongs to a family, a tribe, or a clan. Inserted between these are one or more "middle names" (e.g., Frank Lloyd Wright, Charles John Huffam Dickens, Anne Elizabeth Alice Louise Mountbatten-Windsor), further establishing such family and broader relationships.

If I said "My names are John Malcolm Thomas Fitzgerald Smith" it would sound as if I had two or more identities, or aliases.