To supplement III-AK-III's answer:
Consider the following hadith for usage of ثوب as a blanket:
ولا يفضي الرجل إلى الرجل في ثوب واحد
a man should not lie with another man under one covering
And, as explained in the other answer, there are variants of the hadith which use a different expressions to further clarify what type of cloth is meant:
والله ما نزل علي الوحي وأنا في لحاف امرأة منكن غيرها
By Allah, the Divine Inspiration never came to me while I was under the blanket of any woman amongst you except her
لحاف is defined by Lane's Lexicon:
and from Arabic-Englsih Dictionary by Hans Wehr:
Also Lane's Lexicon is clear that ثوب is often used to mean sheets of plain cloth, and may be used for any form of covering:
...
Similar may be found in the Arabic-Englsih Dictionary by Hans Wehr
The idea propagated by anti-islamic polemics that clothing specific to the female gender is meant is rebutted by other hadith like:
لعن رسول الله صلى الله عليه وسلم الرجل يلبس لبسة المرأة والمرأة تلبس لبسة الرجل
The Messenger of Allah (ﷺ) cursed the man who dressed like a woman and the woman who dressed like a man.