Where do demonyms come from? At times they take -ite, some times -an, -er and this one is jaw-dropping '-siders!'
A person living in New York is a New Yorker (-er)
A person living in Delhi is Delhiite (-ite)
A person living in Sydney is Sydneysider (-sider -OMG! Really?)
A person living in Las Vegas is Las Vegan (-an)
There are innumerable cities across the world and remembering a demonym for each of them does not seem practical.
I don't get demonyms without searching them on the Internet (and trust me, even after searching I fail to get them for some cities' residents!).
This becomes further difficult when the city name is long - say St. Louis, Amsterdam, Rio de Janeiro (Cariocas -full marks who knew this!) and many more.
Is there any way we can assume/know the demonym of the city by looking at its spelling?