ichthyosis

OK, it's not a good thing to have, but it's got a cool name.

https://www.niams.nih.gov/health-topics/ichthyosis

Macarons vs. Macaroons: What's the Difference?

https://www.allrecipes.com/article/macarons-vs-macaroons/

A macaron is a meringue-based sandwich cookie made with almond flour, egg whites, confectioners' sugar, and food coloring. Common fillings include buttercream, ganache, and fruit-based jam.

A macaroon is a drop cookie made with shredded coconut, egg whites, sugar, other flavorings (like vanilla extract), and sometimes ground almonds. Modern macaroons often call for sweetened condensed milk.

Kansas vs. Arkansas pronunciation

A charming young English learner had asked the question.

https://youtu.be/v6P8QmDS0Q4

but here's an answer.

https://www.daytranslations.com/blog/kansas-arkansas/

Endoskeleton vs. exoskeleton

"An endoskeleton is formed on the inside of an animal’s body, while an exoskeleton is formed on the outside of an animal’s body."

http://www.differencebetween.net/science/nature/difference-between-endoskeleton-and-exoskeleton/#:~:text=Summary%20of%20Endoskeleton%20Vs.,and%20proteins%2C%20or%20calcium%20carbonate.

Why is "feather" pronounced like "feet her"?

sleeveen

https://collections.mun.ca/digital/collection/elrcdne/id/51326

Murdoch Mysteries S7:E8 

"He's a charming man, but a sleeveen, I hear." Referring to Jacob Doyle. 

eldritch

I'd never heard this word, even at my advanced age, and with a daughter well-versed in fantasy beings.

Here's the example: 

"He possessed the ability to summon eldritch creatures through a portal to another dimension located in his body."

https://umbrellaacademy.fandom.com/wiki/Ben_Hargreeves_(Netflix)

and the definition:

"Eldritch things are spooky and weird — they make the hairs on the back of your neck stand up."

https://www.vocabulary.com/dictionary/eldritch