Several parts combine into one character.

姑 is a phonetic-semantic compound: 女 (woman) + 古 (gǔ, "old / ancient" — providing the sound). The composite reads as "an older / senior woman" = an elder female relative. The character's precise referent shifts subtly across CJK languages, marking different positions in the kinship grid: in Korean, 姑 means "father's sister (paternal aunt)"; in Chinese, also "father's sister"; in Japanese, "mother-in-law (husband's mother)." The same character, three slightly different aunts.

Korean reading "go." 姑母 (gomo, father's sister — the standard Korean word for paternal aunt; the husband of one's 고모 is 고모부), 姑婦 (gobu, "mother-in-law and daughter-in-law" — used to describe the famously fraught relationship in Confucian Korean households: 고부갈등 gobu galdeung "MIL-DIL conflict"), 姑息 (gosik, "old breath / temporary respite" = expedient / makeshift / kicking the can — used pejoratively for short-term solutions: "stopgap measure").

Mandarin gū, 1st tone. 姑姑 (gūgu, "auntie-auntie" = father's sister — the everyday Mandarin term, doubled like other affectionate kin terms), 姑娘 (gūniang, "young woman / unmarried girl / lass" — a charming Mandarin term that survived from classical usage; used for unmarried women generally and as a polite address to teenage girls), 姑婆 (gūpó, "great-aunt" = grandfather's sister), 姑爷 (gūye, "girl's honored son" = son-in-law). 姑娘 has no exact English equivalent — it carries a slightly old-fashioned, affectionate quality.

Japanese on-reading コ (ko) — 姑息 (kosoku, "expedient / makeshift / kicking the can down the road" — same meaning as Korean), 小姑 (kojūtome, husband's sister / sister-in-law). Kun-reading しゅうとめ (shūtome, mother-in-law) — 姑 (shūtome) names specifically the husband's mother in Japanese kinship. The compound 嫁姑 (yome-shūtome, "daughter-in-law and mother-in-law") is a stock topic in Japanese family-conflict drama, magazines, and counseling — the legendary tension between Japanese DILs and MILs is its own genre.

Memory aid: woman (女) + old (古) — an older woman in the family. Korean / Chinese: paternal aunt. Japanese: mother-in-law.