扶桑 originated in Warring States and Han mythology as a giant mulberry tree in the eastern sea where the sun rises. By the Tang dynasty it became a literary euphemism for Japan, and you'll see it in classical poetry and even modern names (e.g.
严歌苓's 1995 novel 《
扶桑》). Confusingly,
扶桑 also names the hibiscus flower in modern botany — context decides which sense applies.