まんこ

• ま*こ, ま…こ, ま○こ, ま◎こ, ま●こ, ま◯こ, ま☆こ (censored)

Unknown. First attested in the Edo period in the Kantō region, and until relatively recently use was confined to this area. Most likely theories of origin suggest:

• a contraction of 女の子 (menoko, “female child”)
• an alteration of 真処 (mako, “center (of the body)”)
• a shortening of 万幸 (mankō, “10,000 happinesses”)
• an alteration of the Old Japanese みと (mito, “genitalia in general, either male or female”)
• a derivation from the Sinitic 門口 / 门口 (ménkǒu, “gate, doorway”), from a reading of menkō rather than the expected on'yomi of monkō

(Can this⁽⁺⁾ etymology be sourced?)

• (Tokyo) まんこ [máꜜǹkò] (Atamadaka – [1])^[1]
• IPA^(key): [mã̠ŋko̞]

まんこ or マンコ • (manko) 

1. (vulgar, slang) female genitals: a cunt, a pussy

   オマンコ

   omanko

   (affectionate) pussy

   • 2017, “セックス大好き”, performed by Pink Guy:

     マンコは気持ちいい/ぬるぬるしていい

     manko wa kimochīi / nurunuru shite ī

     pussy feels good / it's really wet

2. (Internet slang, derogatory, offensive) a woman

   フェミマンコ

   femimanko

   femcunt

• Only used as slang. Never in medical situations.
• Considered harsher than おまんこ (omanko).

• おまんこ (omanko)
• やりまん (yariman)
• ちんこ (chinko)

Appears to be specific to the Tsugaru dialect spoken at the northern end of Honshū.^[2]

Full derivation unknown. The final こ (ko) is almost certainly the nominalizing suffix, but the preceding まん (man) is uncertain.

• IPA^(key): [mã̠ŋko̞]

まんこ • (manko) 

1. (dialect, Tsugaru) a ruby (gemstone)

   Synonym: 紅玉 (kōgyoku)