"Marjory is really hot."
Translation:Tha Marsaili gu math teth.
Teth means actually hot, like a fire, a teakettle, a summer day.
“Hot” meaning “alluring or desirable” is an idiom only in English. There’s no reason why it would carry over into any other languages, lol.
EDIT: Apparently the idiom “hot” = “desirable” occurs in a few other languages, as mentioned in comments below. But it’s still not something one can assume exists in every other language just because it’s used that way in one’s own language. Idioms notoriously do not translate in most cases.
And it's just how people speak these days. It would not be at all unheard of to have someone make a comment like that about someone's appearance.
Oh, and all of the languages (with the exception of Arabic) I'm studying on Duolingo have had sentences related to underwear or the like.
(Btw, ribald = great word choice!)