Well, we do have some more polite equivalents... "Co [do/u] [diabła/licha/diaska]?!"
"Co [do/u] diabła?!" is like "What the devil?! (Nominative: diabeł)
"licho" is rather a dated word, that may be some kind of a demon bringing misfortune, or it can be the devil
I have no clue what actually "do diaska" means, it is just used like that. Maybe it's more an expression of anger though...
To summarise Jellei's comprehensive answer to this popular question:
Polish has three closely-related verbs:
- nosić: to wear; to carry
- mieć na sobie: to be wearing (lit. "to have on oneself" right now)
- nieść: to be carrying
Polish treats to wear | to be wearing (Present Simple | Present Continuous) as a Verb of Motion, fewer than ten Polish verbs that actually distinguish between the Present Simple | Present Continuous) aspects. So wearing is wrong here: it's the correct translation of ma na sobie (not officially taught on this course).
[20 Feb 2019 08:56 UTC, ed. 20 Jun 12:03 UTC]
As MrLEGOChaley says further down, it's apparently part of Duo's philosophy to include weird sentences, which are intended to help us remember vocabulary and even grammar. It doesn't usually work for me – with the exception of "To twój słoń!", which I rather remembered by my own method of imagining a context for its use, e.g.:
"It's your elephant! You can feed it, pick up its poo, and pay for what it did to my kitchen!"