Some Koreans argue that Nara, one of the ancient cities in Japan, has etymology in the Korean word nara, which means country. But they make a fatal mistake: They compare the present forms. As a matter of course, every language is constantly changing. When we compare two languages, we should trace them back to the old forms. Then what is the old form of the Korean term of nara?
Due to fragmentary data, it is almost impossible to reconstruct the Old Korean language (?-10C). The form of nara of the time when Nara was founded is still unknown. But nara can be traced back to the Middle Korean form: narah. Narah appears in Korean documents such as Wolinseokbo  (1459) and Beopwakyeong-eonhae  (1463). And according to the famous Korean linguist Yi Ki-mun, the much older form may be narak.
As you know, Japanese is an open-syllable language. Every syllable ends in a vowel, except for "n," which is considered an entire syllable and thus can precede another consonant. Loan words into Japanese are also adjusted to fit the required syllable shape of Japanese, by inserting vowels to break up consonant clusters, or inserting a word final vowel to prevent the occurrence of a word-final consonant. So if narak was borrowed into Japanese, it should have been changed into naraka or naraku, not nara.
Here is another wordplay. A Zainichi (residing in Japan) Korean, Kim Tal-su (1919-1997), asserted that a Korean term "wasso" [has come] is the origin of Japanese "wasshoi", which people shout as they carry mikoshi (portable shrines) at festivals. Since then, it has been spread as an accepted theory by many Korean and is becoming a folk etymology. Korean do as Joseph Goebbels said: Repeat a lie 100 times and it will become truth.