豆腐西施

This idiom describes someone (usually a girl) who looks very charming but does poorly or behaves poorly behind the scenes; however, the meaning of the username doesn't need to be negative necessarily. Sometimes people just choose classic elements to highlight beauty and cultural traditions. There's probably someone named 'Xishi', a well-known beauty figure in Chinese culture, related. And this phrase could also playfully describe oneself as an ordinary person doing small deeds with charm.