"kuiken" is Dutch for a chick, a young chicken (curious that in English, the form with the diminutive became the one used for the adult), whilst "kieken" is dia

"kuiken" is Dutch for a chick, a young chicken (curious that in English, the form with the diminutive became the one used for the adult), whilst "kieken" is dialectical Dutch for "chicken". "kieken" and "kuiken" come from the same root, it's just that one of them got mutated by a sound change that never quite spread over the entire language. "jongen" is another story. It used to be "jonge", which is the substantivized version of the adjective "jong" (young). The -n was later added by analogy from the other cases. This is why the plural is pronounced "jonges" (written "jongens"), and the diminutive is "jongetje" even in the standard language.