What's the meaning of the phrase 'Back seat driver'?
Someone who criticizes from the sidelines.
What's the origin of the phrase 'Back seat driver'?
This comes from the annoying habit of some people of giving unwanted advice to vehicle drivers. It emerged in the USA in early 20th century, as motoring was becoming widespread.
Before the phrase took on its figurative 'unwanted adviser' meaning it had been used as a literal reference to people who drove vehicles from the back seat.
The first reference I can find to someone being called a 'back-seat driver' refers to that literal usage and is from the Daily Kennebec Journal (Augusta, USA), May 1914:
"When New York pitcher Vernon Gomez retires as a smokeballer he wants to become a smoke eater. Here he gets a tryout as a back-seat driver on a hook and ladder truck at St. Petersburg..."
Throughout the 20th century U.S. fire departments commonly used large articulated ladder trucks, known as tillers. These had both front and rear-wheel steering to enable the long vehicles to turn in city streets.
The link between that form of back seat driving and the present meaning of the phrase isn't explicit, and there's no particular reason to attach any negative sentiment to it. It's possible that the phrase originated that way, but I rather doubt it.
The figurative and derogatory meaning of 'back-seat driver' is unambiguous in this from piece from the Oklahoma City Star, August 1914:
He did not see the car till I screamed (and I'm not a back seat driver either) but I knew that he did not see it, so it was time to do something.
The usage there suggests that the writer would have expected readers to be familiar with the term.
The expression must have been in common use, in the UK at least, by 1930, when P. G. Wodehouse used it, without any explanation of its meaning, in Very Good, Jeeves!:
Quite suddenly and unexpectedly, no one more surprised than myself, the car let out a faint gurgle like a sick moose and stopped in its tracks ... the back-seat drivers gave tongue. "What's the matter? What has happened?" I explained. "I'm not stopping. It's the car."
We no longer need back-seat drivers in cars to nag us if we take a wrong turning; we now have electronic devices for that. I wonder how long it will be before someone coins a negative term for them?
See other phrases that were coined in the USA.