Not sure if this is semi-common knowledge or not, but:

I’m sure everyone is familiar with at least one of the geographical adjectives for the cardinal directions: Oriental, generally meaning eastern.

Similarly, you can probably see the connection for the North: Boreal. As in Aurora Borealis.

Known to a lesser degree, there is Occidental, meaning western. I don’t have a connection for this one off the top of my head.

And finally, for the sake of this comment, there is the term for the South: Austral. Of course, this is where we get “Australia.”

As such, the magnetic light show of the Antarctic is not aurora borealis. It is, in fact, aptly named aurora australis.

Another fun side note: There was allegedly support for the idea of naming Canada Borealia. I personally like this idea, because it tickles my inner 12 year old.

The word ‘dog’ is interesting because it essentially has no etymology. It has no known cognates in English/Germanic/other Indo-European languages. It first showed up in Old English as dogca, referring to some sort of mastiff, but other than that nobody really has any idea at all where it came from.

Muscle comes from latin and means little mouse.

Tried and True.

To you it probably means “tested and found to be reliable/trustworthy.” An example, a few days ago the topic of a car without hydraulic brakes made the rounds. Hydraulic brakes on passenger cars are “tried and true,” we trust them, and are skeptical of a vehicle without them. But that’s not where the phrase originally came from; it’s a centuries old woodworking term.

This is a try square. An OLD tool; examples survive from ancient Egypt. It’s such a basic tool that it’s often used as the symbol of the carpentry trade. “Try” in this case means “examine” rather than “attempt”, more like how a judge “tries” a case than a jedi trainee “tries” to lift an X-wing out of a swamp. A try square is used to examine a board. For squareness, and possibly also straightness and flatness. A board that passes this exam is said to be “true.”

“True” meaning straight, flat, parallel or even concentric is still in use to this day; “truing” a surface means to flatten it.

Care means ‘heart’ in french Coeur.

A hassle is a foreign inclusion in a wool top (what is spun into yarn), which is a real hassle to remove.

A skanky fleece is a wool fleece that is matted and infested with maggots.

The terms date back to the 19rh century.

“Helicopter” isn’t heli - copter

It’s helico - pter.

Helico: Greek for helix or spiral.

Pter: Greek for wing, like a pterodactyl.

Either „tea“ and „cha/chai“ exist in some form virtually every language that has encountered tea, and the distinction between which was adopted generally has to do with whether it was first traded with the country by land (cha) from China or by sea (tea) from Malaysia.

In Russian the days of the week are mostly numbers, e.g. Tuesday is the second day, so Tuesday is Вторник, which comes from второй (second) and the suffix -ник for day. But Monday is not перник as you would expect (первых + ник), instead Monday is Понедельник. This is short for после (after) не (not) делать (doing) -ник (day), i.e the day after not doing anything (Sunday).

In Finnish a tietosanakirja is an encyclopedia, this is a composed word made from tieto (knowledge) and sanakirja (Dictionary). But also sanakirja is a composed word made out from sana (word) and kirja (book). So an encyclopedia is a book of words of knowledge.

‘Bully’ used to mean good friend. There’s a scene in Shakespeare (who else?) where he talks about someone sending his bully boys to teach someone a lesson, meaning he sent his close friends. But, over time, people took it to mean his thuggish friends and so the word’s meaning shifted.

The term “snorkel” derives from the German word for snoring.

Back in WW2, U-boats (and pretty much all submarines) needed to surface so that they would be able to run their diesel engines in order to charge their batteries because diesel combustion requires oxygen. One German scientist developed a way to get air without having to surface the boat. As this was a very big tactical advantage it was, obviously top secret. In order to not give away what it was, he referred to it by the sound it made i.e. that of someone snoring.

Proto-slavic used the root “dn” (дн) for water, which explains river names such as Dnipro (Дніпро,Днепр), Danube (Дунай/Donau), Don (Дон), Dnjester (Днестр, Дністро).

“Son of a gun” is from when sailing ships would come into port. The sex workers would row out to them and have sex with an entire gun crew.

When the kid was born they didn’t know who the father was so he was a “son of a gun” aka a bastard.

The word “slogan” comes from a swedish word meaning “battle cry”.

Denim= De Nîmes (from the city of Nîmes)

Jeans = Gênes , the French weird for Genoa.

The cotton weave, indigo dyed cloth originated in Genoa, and in France the main production centre was Nîmes.

So ‘denim jeans’ is both a tautology and a contradiction