Today is the yahrtzeit of R' Elimelech m'Lizensk, so a bit of "machshava":
The letters Mem-tzadi represent concealment. The Berdichiver explains the word Mitzva to be a reflection of the shem Havaya - the last two letters are obvious, but the first two letters are concealed: mem-tzadi is at-bash code for yud-key. Part of the function of a mitzvah is to reveal the yud-key which is hidden and unite it with the vuv-key.
The Maor V'Shemesh writes that man and matzah are opposites - the 40 years in the midbar when man fell were marked by no korban Pesach and hence no real kiyum of achilas matzah (certainly acc. to the opinion that it would be derabbanan, but even if d'oryasa, not a full kium). When Klal Yisrael come to E.Y., they renew the korban pesach and at the same time the man stops.
Based on the Berdichiver, we can explain this phenomenon: man=giluy, lechem abirim, food of the malachim bestowed directly by Hashem to the dor de'ah. The mem-tzadi of matzah=kisuy, hester. They can never go together. During the 40 years of the dessert Hashem's presence was fully felt, but with the return to Eretz Yisrael came a return to life led b'derech hateva, where Hashem's presence must be revealed by man, and eating matzah returned as well. The goal, however, is to realize that matzah and man are one and the same - matzah is man in potential, waiting to be revealed for what it is.
With this we can better explains the question of the gemara in B.M. 86, "Did the Malachim who came to Avraham really eat"? There is no a priori reason that a malach cannot eat (in fact, Tos. brings a Midrash that they did eat - hard to imagine a machlokes in metziyus). Rather, since the essence of a malach=giluy ratzon Hashem, it cannot absorb the matzah=hester, concealment.
The Ba'al haTanya teaches that Chochma=koach m-h, the power of "what", the smallest degree of intellectual awakening in man. Matzah= this power of chochama, m-h, but with the letter "tzaddi" in the middle. The Noam Elimelech (p' noach) explains that the letter 'tzadi' is a combination of 'nun' and 'yud':yud=the smallest letter, occupying almost no space yet also representing a complete unit, represents the tzaddik, who channels Hashem's munificence to the rest of the nation, represented by the letter "nun", which has a narrow top but a wide base, as the haspa'ah lows downward to the masses. The hashpa'ah that flows down to the 50 levels of 'nun" must be channeled and flow through the tzaddik to be realized. By pesach mitzaryim, the 'mah' of chochma had to be channeled through the tzaddi so it was accesible to the hamon am, hence the food became 'm-tz-h'.
In the midbar, once we were elevated by a yetziyas mitzaryim, that same chochma became 'man' - it went directly to the 'nun', it was accessible to even those on the lowest madreigos without needing the yud on top, the tzaddik, to be mavarer the hishpashtus first.
This perhaps is the meaning of the pasuk 'Va'yikr'u es shmo man ki lo yad'u mah hu'. They called this food of the malachim with the new name 'man' because they didn't realize it was the same 'mah', meaning koch mah, the same bechina of chochma found within matzah.