西瓜姑娘
[xī guā gū niáng]
'Watermelon girl', a sweet and simple nickname which could imply someone has freshness or sweetness associated with a watermelon, like innocence of youth or being easy-going and cool as summertime treat. It could also refer someone with round shape akin to watermelons if describing physical appearance though it depends largely upon personal contexts surrounding choice of usernames for social use cases.