If you do any winter recreational activities you've likely seen them:
I think it is actually common English, it just depends on people's age and location. I live in the UK and have never, ever heard anybody call a "beanie" anything but - but I grew up in England in the 90s/2000s so "beanies" were and still are very popular with the Emo / Skater types.
I have a propellor beanie. Sometimes I hook the little electric motor on it up to a watch battery and let it spin and spin.
But the term beanie, meaning a knit cap, is a new thing to me that, since I've been taking this course, I'm starting to see with greater regularity. I'm considering asking my knitter wife to make me one, so that I can hook up another propellor to it.
It seems the overall consensus here is that "beanie" is not a word that the majority of us use, or have even heard of. It sounds like its greatest usage is in Australia, and the Northwestern USA? It makes me wonder where the Duolingo employee who came up with this translation is from...
I'm American and have lived in 7 states across the Northwest, Southwest, Pacific Southwest (ie Hawai'i) and Midwest and have never heard this item called a beanie! several places with cold winter weather are on my list. The terms for this hat are definitely regional. I'm glad I read this chain because now I know to what it refers!
I grew up in South Dakota & have lived in a dozen states in the West, Northeast, New England, & South. Beanie was a new word for me - I grew up calling it a stocking hat. So yeah, definitely a regional term - it's interesting how many different words people have for it. I wonder why - we all say gloves, mittens, boots, right? Not many (if any) regional variations on most articles of clothing.
I'm American and we rarely use beanie. As noted above, it's either the small hat with propeller like Calvin's. [http://www.freerepublic.com/focus/bloggers/3140434/posts], but is becoming more commonly used for a snugger fitting knit cap popular in sportswear. As a knitter, I see patterns for luer that are what we would call stocking caps/hats. (At least here in Minnesota).
I thought of that strip as soon as I saw the word beanie. (Although, to me and everyone I know, a beanie is a knitted cap, and I live in Michigan).