@DY that’s not quite right. In yiddish an aleph is used for kamatz or pasach sound (almost like vowels in English), and an ayin for a segol sound when using a native Yiddish (or German or English) word. Hebrew words are usually written in their proper spelling especially if they’re clearly not Yiddish in origin.
(Exceptions include שאבעס for שבת but even that spelling is not usually used and even then only to show that it’s the “heimish” pronunciation.)
So נאר is “nohr” which means only, whereas נער in the first version is clearly the Arameic word (for fool, the line means “on’t be fool”) and so would be written with an ayin.
All the IIRC.