I'll give it a try. Europeans gave them these names. Europe and the Mediterranean area had Cedars species which had aromatic wood, and Cypress species which had not so aromatic wood. These trees were called this first, obviously a long history in that part of the world with Rome, Greece, Middle east...

So when Europeans explored the other parts of the world, they did not known what these different trees were called (nor did not care what the native people called them) but noticed they were somewhat similar so they compared the wood to Cedars and Cypress. They called aromatic wood "cedars" and non-aromatic wood "cypress". Confusing, but they were more interested in using the wood than evolutionary relationships.

Because early colonists in North America found trees with scented wood, and wrongly assumed they were the same as the cedars with scented wood that they read about in their bibles. At the time, cedars hadn't yet, or had only recently, been introduced to cultivation in western Europe (Lebanon Cedar reached Britain in 1638), so most people wouldn't have known what real cedars looked like.

Actually, Mediterranean Cypress also has scented wood, but this fact isn't mentioned in the bible, so people didn't know it. Important to bear in mind that at that time, for most people, the bible was pretty much the sole source of information about the eastern Mediterranean (or anything, outside of their immediate experience).

What's really sad is the failure of subsequent education to correct the error. Time to get it sorted!!

Resin

That makes sense. Although lots of other misnamed trees have been "corrected" over the years - these weren't.

I guess it's not as bad as the fact that 90% of the people I know call any needled conifer a "pine" whether it's a Pinus, Abies, Pseudotsuga, Picea, or whatever.

On a side note - I don't know whether to be fascinated or saddened by the fact that so much knowledge was only available from the Bible for so long!

Nothing against the Bible, I read it, although I'm not the most devout Christian...but geez - there are other books!

"I guess it's not as bad as the fact that 90% of the people I know call any needled conifer a "pine" whether it's a Pinus, Abies, Pseudotsuga, Picea, or whatever"

Must admit, I'd say it's worse - Abies, Pseudotsuga, Picea, etc., are all in the pine family Pinaceae, so calling them 'pines' has a degree of logic. Just like Taxodium is called a cypress; although not a Cupressus, it is (as DNA has now shown!) in the cypress family Cupressaceae (Linnaeus even first described it as Cupressus disticha). Or that every genus in the family Arecaceae is called a palm. But calling a cypress a 'cedar' is more comparable to e.g. calling a pine a 'juniper' or an oak an 'elm'.

Resin

Well, Resin, that's true...except for Norfolk Island Pine...