I’m probably far from the first person to make this connection, but Noonien seems like a pretty obvious phonetic misspelling of Nguyen to me. I last watched TOS and a lot of material related to Khan as a kid and I don’t know too much about Roddenberry as a person, but given his other stances I think it’s not impossible that this is his “hidden” commentary on the Vietnam war. And even putting all of that aside for a moment; his “friend” (if he really existed) might’ve been ethnically Chinese, but born in a different Southeast Asian country and the native language there then adapted his Chinese name to fit their phonology. But I don’t know, I’m not a professional linguist, I might be way off here… (Ah I just saw Deceptichum had pretty much the same thought as me but was faster in writing them down ^^')