"My skull caps."
Translation:Οι σκούφοι μου.
Yes, I found the same when I googled it, but still have never seen the term. Maybe I should narrow down my location from North America to Southern California. I'm sure it's used throughout the world where temperatures are cold, but I've never heard it here in hot So-Cal. Anyhow, just a suggestion that your team might want to consider for people who are from warmer climates, instead of "skull cap", use "hat" or simply "cap".
It is frustrating to try to guess what meaning you are going to give this word next. Sometimes "cap" seems to be accepted but this time when I used it I was corrected to "winter cap"!?? I want to learn the Greek so I don't care what meaning, even incorrect, you give to the English word as long as it is consistent. But, for the purpose of the English note:
(Collins English Dictionary - Complete Unabridged 2012 Digital Edition)
hat, noun 1. any of various head coverings, esp one with a brim and a shaped crown
cap, noun 1. a covering for the head, esp a small close-fitting one made of cloth or knitted
That is: hat and cap both are simply head coverings, with one being more likely to have a brim than the other.
Trying to force a distinction that doesn't exist in English is just causing confusion. I don't know what the answer to this problem is, and in looking into it I noticed that there are problems in the Duolingo community with hat, cap in many other languages.