Chinkie is a very unkind name for a Chinese person. Do not use it. It is a slur: it takes a whole group of people and turns them into a nasty nickname. People have used it to insult, to shut others out, and to make harm sound smaller than it is. You may still hear it in old films, in ugly jokes, or in a few places as a crude word for a cheap Chinese takeaway — that use is insulting too. If you see it in a book, it is there to show hate or old prejudice, not to give you a word to copy. There is no polite way to say this word. If you need to talk about where someone is from, say Chinese, Taiwanese, or whatever is true for that person.