If 白玉 (shiratama) means “white gem,” “pearl,” or “rice-flour dumpling,” what happens when you add 楼 (watchtower)? Here’s what you get:
白玉楼 (hakugyokurō) white + jewel + watchtower
The rarely used (and pedantic-sounding!) compound 白玉楼 refers to a dead literary figure and was initially used in China for a dead poet.