Why Is It Called A Fifth Wheel?

Have you ever heard someone refer to a fifth wheel and wondered why it was called that? A fifth wheel is an important concept in engineering, and its name comes with a fascinating history.

In this article, we’ll explore the origin of the term “fifth wheel” and how it applies in the world of engineering. We’ll also uncover some lesser-known facts about fifth wheels, including how they are used in modern automobiles and how they can be used to add an extra layer of safety and convenience to your car. So join us as we unravel the mystery of the fifth wheel – a key part of automotive and engineering history.

Why is it called a fifth wheel?

A fifth wheel is a slang term that is typically used to refer to someone who is the extra person in some kind of relationship. The slang is thought to come from the way that carriages of the 19th century were designed, with solid disks attached to them to support extra weight.

In this context, the extra person is seen as the fifth wheel – attached to the relationship carriage, but not essential to the running of it.

Early Origins of the Term “Fifth Wheel”

The term “fifth wheel” first appears in writing in the late 1700s, but its meaning was different to what it means now.

Back then, the term was used to describe someone who was a hindrance or an unnecessary burden to a situation. It wasn’t until the 19th century, when the carriages of the day were designed, that the term began to be associated with the extra person in an otherwise intimate situation.

The Breakdown of the Carriages of the 19th Century

Carriages of the 19th century were designed with four wheels and one solid disk attached in the middle. The disk was designed to help support heavy loads, and the carriage was able to cope with the extra weight without tipping over or becoming unstable. As a result, the extra weight became known as the “fifth wheel”.

Applying the Term to People

The phrase “fifth wheel” was soon applied to people, as those in the social circles of the day began to observe the dynamics between couples. Often there would be a person in the group who was seen as the extra person, or the “fifth wheel”. This could be a friend of one of the couple, or someone who was interested in one member of the couple, but wasn’t essential to the relationship.

The Modern Usage of “Fifth Wheel”

Today, the phrase “fifth wheel” is still used to refer to someone who is the extra person in the relationship, although in a more jocular and less sinister way than before. It is most frequently used to describe someone who finds themselves in an otherwise intimate situation, or an ‘outsider’ within a relationship.


The term “fifth wheel” is an old phrase which was originally used to describe someone who was an unnecessary or intrusive burden to a situation, but which has since been applied to someone who is the extra person in a relationship. The phrase has its’ origins in the carriages of the 19th century, as they were designed with four wheels and a fifth solid disk, which was designed to help support any extra weight. The person who was the extra in an intimate situation was soon seen as the “fifth wheel” in the relationship, and this phrase is still used today but in a more humorous rather than sinister sense. Citation URL: https://www. yourdictionary. com/fifth-wheelhttps://idioms. thefreedictionary. com/fifth+wheel

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