The word "boninesses" itself is not very commonly used, but there are a number of synonyms that convey a similar meaning. For example, "emaciation" and "gauntness" both suggest a lean or bony appearance, often as a result of malnourishment or illness. "Scrawniness" and "lankiness" also describe a thin or skinny physique, while "skeletal" implies an almost skeletal-like appearance with visible bones. "Spareness" is another option that suggests a lean or thin build. Overall, while there are several words that can describe bony or thin physical characteristics, it's important to use them carefully and with sensitivity, as they can carry negative connotations.