שמואל א יט:כד פירוש: רש״י

He too removed his garments. His royal garments, to put on his students' garments.

He fell down stripped. Targum Yonoson renders וּנְפַל בִּרְשַׁן 'and he fell naked.' And in the name of R. Menachem, who heard from an Arab, בִּרְשָׁן in Arabic [means] insane.