姑

Woman radical on the left - depicts a kneeling figure with crossed legs, the classic seated-woman silhouette. Carries the meaning of 姑: a female relative on the father's side - paternal aunt, sister-in-law, or by extension a young unmarried woman. Same family: 妈 mother, 妹 younger sister, 姐 elder sister, 婆 grandmother - the whole female-kinship inventory.

Right side 古 supplies the sound - gǔ shifting to gū, a regular tone change. The 'ancient' meaning of 古 has a faint cultural echo here: the paternal aunt was traditionally a senior, respected figure in the extended family, the elder woman whose authority over young brides was almost mother-in-law-like. Same phonetic in 估 estimate, 故 reason, 苦 bitter.