Fun fact: Watermelons are from Africa. West Africa actually.
Also, in Hungary (I'm half Hungarian) when someone is a bit "down" people ask "Mivan? Nem kaptàl dinnyeföldet?" Which basically translates into something like "Wha? Didn't you get your watermelon field?". It's a jest and people laugh at it, but back then I didn't get the point. I laughed with the others because I knew it was a joke, but the story is a bit sad actually.
Back in the day when the poor peasants needed some extra money they could rent a bit of a field from a rich person and grow watermelons to sell them. Thing is, if you were too late you were, well, too late so no watermelon field on you and thus no extra money to feed yourself and family, and thus the term.
Funny story that the PC/SJW crowd will hate, but here goes:
I went with an x-band member to his place before a bad session and there was this black guy there. I was a bit tipsy and I looked at him and just said "What's up, my nigga?". He looked at me first and then just laughed hard. I am a ginger and also pretty skinny, so my nick name was "bony ass" and "pale boi" and we laughed and we joked about stuff like that. Who got OFFENDED!!!!??? Well, white SJW/PC guy.He came to me (way later) and said "I'm offended! You should never have said that!". And for me, since it was all just a joke, I asked "What? Didn't you see that we were joking and having a good time? He is not offended, so why the phuck are you?" His answer was something like "I'm offended for him." This is the problem with the PC/SJW crowd: Attention seekers.
Anyway, a week later I went back and saw "my nigga" again and we just looked at each other with BIG smiles. The joke was still on ;) BUUUT, I didn't catch his actual name the first time, so I got a bit tricky and asked "Yo. I didn't catch your name last time. What do you WANT me to call you?" (A very intentionall question) and he just looks at me and says "Chocolate Boy!"
For the first time in my life I had no instant comebacks. He won. He won fair and square. DAMMIT!
Anyway, we laughed a lot. HAd a couple of beers and became good friends. White /PC/SJW boy still hates me though.