Asklemmy

Penultimate. I used it as though it referred to the last thing rather than the second to last thing.

When I was younger I thought concur meant disagree.

ages ago, i spent something like half a year thinking there was a word "appericate". it was an odd one, since i only ever saw it in print, and from context it was clear that it meant the same thing as "appreciate", which, oddly enough, i only ever heard in speech.

and then one day i stopped at an "appericate" in a book and re-read it 9 times, very slowly.

Terrence Thatcher, T. May, Terroris, Ttruss;
Terry-Tories, Terry-Tories, make a fuss!

It also gives a different meaning to the citizens of British Overseas Tories!

"Sorry."

It took me until graduate school to learn that "mortified" is not another word for "scared"/"fearful"

It still looks that way to me what with mort in there!

It also took me a long time to realize that the word "awry", which I read often in books and inferred its meaning, and "ah-rai" were the same thing. I thought awry was pronounced "aw-ree" and it was just a synonym for "ah-rai".

Man, I'm learning some weird stuff about British people. I've never heard of encephalitis being associated with HIV or a nonce being any kind of person.

Not a word but I thought the idiom toe the line meant basically the same as push the envelope. As in you're testing the boundaries of something by walking right up to the line and nudging it with your toe to move it further.

Turns out it means pretty much the opposite, essentially the same as fall in line.

Portuguese ⟨bisonho⟩. I always used it as "needy", "demanding excessive attention" (like a child). Until someone informed me that it was supposed to be "weird".

With English as my second language, the difference between terrible and terrific has always confused me.

The word "nauseous" is parallel to "noxious" and means "causing nausea". If you're experiencing nausea, you're nauseated -- the thing that made you nauseated is nauseous.

I don't use it very often but I misuse the word "Gattaca" on purpose sometimes. In reality it's the title of the 1997 film that's named from the letters G,A,T, and C, referring to guanine, adenin, thymine and cytosine, the four nucleobases of DNA.

But on the TV show The League, the character Rafi (Jason Mantzoukas) screams it as his battle cry during paintball, completely oblivious to what it actually means or that it's the title of a movie. I urge you all to misuse this word at some point as well -- if you ever need to hype yourself up, try screaming "GATTACA!" as your battle cry!

Callow. It just means immature but I somehow got it in my head that it meant cowardly.

Inconceivable!