it is a non-sanskritic word because there is no bengoli equivalent of it... and western assam (goalpara side) i think no one uses it or if they do it is because of upper assam influence.. my theory is that it comes from the tai word khér lawn (which to non-native years can sound like khi-lon .. just like tsēr sound to many ppl as 'chi')

the word khér / xér means ethnic or indigenous people of some area and lawn / don means hill or literally mountain tribe or hill tribe... the ending -ia suffix is just assamese thing.. like Tai Aiton people area called as 'Aitoniya' and so on..