1)
What is "Ploni Almoni"?
1.
Rashi citing Targum Yonasan: It is covered and hidden. Ploni is like "Ki Yipalei" (Devarim 17:8); the Targum is Yiskasei (is covered). Almoni is anonymous; he did not want [the identity of the place] to be revealed. Mahari Kara - it is like Ilem (mute).
2)
What is the meaning of "Tachanosi"?
1.
Rashi: I will camp there [to ambush Melech Yisrael, or his troops coming to plunder in my land].