おかま

Compound of 御 (o-, “honorific prefix”) +‎ 釜 (kama, “pot”);^[1] compare Kunigami ふぁーま (fāma), ふ’かーま (fuk'āma), わはーま (wahāma), Miyako うかま (ukama).

The development of the slang senses appear to have started from an analogy comparing a man's butt to the shape of certain pots.

• (Tokyo) おかま [òkámá] (Heiban – [0])^[2][1]
• IPA^(key): [o̞ka̠ma̠]

• (Kyoto) おかま (Teiki – [0])^[1]

おかま or オカマ • (okama) 

1. (formal) Used other than figuratively or idiomatically: see お,‎ 釜,‎ 竈.
   1. a cooking pot
2. a steam locomotive
3. a volcanic caldera
4. (dated) one's wife
5. (archaic) a serving woman, a female servant
6. (slang) someone's posterior or butt, particularly a man's butt
7. オカマ: (slang, LGBTQ, often offensive) loosely, any man viewed to be homosexual or effeminate:
   1. a gay man; a male homosexual; a faggot
   2. a trans woman

The word o-kama makes no actual distinction between the senses of "gay man" and "trans woman"; both senses are under the same category of "effeminateness". This means that when referring to a "trans woman", there is no explicit allusion to real gender identity, and the word could just as easily be applied to a cross-dresser, etc.

• お焦(こ)げ (okoge, “burnt residual food; fag hag”)
• おなべ (onabe, “masculine woman; (butch) lesbian; trans man”, literally “stew pot”)
• オネエ (onē, “an effeminate man”)