noun
innate character; spirit; backbone
Refers to a person's deep-rooted nature, moral fiber, or resilience. Often used in expressions like 土性骨が曲がっている (to be crooked by nature) or 土性骨が据わっている (to have a firm character).
彼は土性骨が曲がっているから、何を言っても無駄だ。
He's crooked by nature, so it's no use saying anything to him.
あの人は土性骨が据わっ
That person has a firm character and is unshaken by any hardship.
Ateji compound using 土 (earth), 性 (nature), and 骨 (bone) to phonetically represent どしょうぼね, suggesting a person's fundamental, earthy character and inner strength. The exact historical derivation is uncertain.