Okay fine, the Korean doesn't really want to study right now. Here's a short one.
My mom was telling me about the way that Koreans describe an ugly woman as a "호박꽃," but she didn't know where it originated from. Could you possibly find out how it came about? She hates the metaphor because she thinks it's contradictory to describe any flower as ugly. She also had me take a picture of one in our backyard to show people that it's really a beautiful flower.
Zucchini flower fan
Dear Zucchini flower fan,
Your mother is right: zucchini flowers are pretty (like the one in the picture you sent), and it would make no sense to use the word to describe ugly women. Truth is hobak-kot (that's what the hangeul in the question says) is not a zucchini flower at all.
The correct euphemism is neulgeun hobak, rather than hobak-kot. The word hobak is somewhat confusing because it means both pumpkin and zucchini. (Often Korean people use the term ae-hobak for zucchini to distinguish the two.)
For the euphemism, the correct meaning is pumpkin, not zucchini. The word neulgeun means "old". So now the euphemism makes sense -- ugly women are like old pumpkins, because old pumpkins are fat, bumpy, and wrinkled.
By the way, the euphemism is the same in Japanese as well, which contributed to a subtlety that was understood by few in Memoirs of a Geisha. A friend of the main character Sayuri is called "Pumpkin". That doesn't mean that she was cute, as Americans might understand it. (Al Bundy always calls his daughter Kelly "pumpkin" in the sitcom Married with Children, which always cracks the Korean up.) Basically Sayuri's friend was called "Ugly" her whole life, which makes her actions after the war a little more understandable.
How did we get to hobak-kot from neulgeun hobak? First, the neulgeun part is often dropped, and calling an ugly woman hobak is enough to convey your less-than-good intent. But calling someone a hobak straight up is a little too mean. So the euphemism is softened up a bit into hobak-kot, the "pumpkin flower," since women are associated with flowers. So the euphemism is not really a knock against the actual pumpkin flower -- it's just a derivation from calling someone a "pumpkin".
Got a question or comment for the Korean? Email away at firstname.lastname@example.org