The phrase “Yom Yerushalayim” is first mentioned in Psalms 137 verse7, 3 thousand years before the 6 day war. Where does the name Yerushalayim come from? The answer is given by Tosfot in Tractate Taanit, 16 who state that the name Yerushalayim is a combination of two words, one uttered by Avraham at the Akeda (Bereshis 22), "Har Hashem Yeiraeh", which means "The mountain where G-d will be seen", and the city was already called Shalem, (peace), by Malkitzedek (Bereshis 14).

Thus, the city of Yerushalayin combines the two names, given by these great people, Avraham and Malkitzedek – "Yeiraeh" and "Shalem". Tosfot also explain that  the reason we don't put a YUD between the LAMED and the MEM in the word Yerushalayim,  is that we focus on the name, Shalem, which means peace and has no YUD. 

The former Chief Rabbi Yisrael Meir Lau stated that the name Yerushalayim appears 667 times in NACH, and only three times in NACH do we find  the word Yerushalayim spelled with a YUD MEM at the end of the word. Isn't it an amazing coincidence that the IDF reunited Yerushalayim on the exact non-Jewish month and year 6/67? We know that there are no coincidences. Thus, the word for coincidence in Hebrew is MIKREH, spelled MEM KUF REISH HEH, which rearranged spells "RAK MEHASHEM", only from G-d!

The question now arises why we pronounce the word Yerushalayim with a YUD when the vast majority of times it is written without the final YUD? The answer is that the PATACH YUD MEM ending in Hebrew makes the word dual, for example, "OZNAIM" (ears), "RAGLAIM" (feet), "YADAIM" (hands). The above question is answered by the Talmud which explains that there are two Jerusalems, a heavenly one which is situated directly above the earthly Jerusalem. Just as the heavenly Jerusalem is G-d's eternal capital, so is the earthly Jerusalem, Israel's eternal capital, despite the objections of the U.S. State Department and UNESCO.

Samuel II: Ch. 5 states that Jerusalem was Israel's D.C., which stands for DAVID'S CAPITAL, three thousand years before Washington, D.C. was the capital of the U.S.A.  Jerusalem will remain Israel's eternal, undivided D.C. capital despite the objections of our so-called "peace partners" and the United Nations.