What is the meaning of "Yachil"?
Rashi: It is [to make tremble,] like "Chil ka'Yoledah" (Yirmeyah 6:24). Malbim - it is as if the Midbar came on the birthing stool, and the birth pangs frenzy it to expel what is in the earth's 'stomach', full of fire, sulfur and flame.
Radak (11): It will pain. This is a metaphor - "v'Chol ha'Chelkah ha'Tovah Tach'ivu ba'Avanim" (Melachim II, 3:19). We find also "mi'Lifnei Adon Chuli Aretz" (below, 114:7).
Why does it mention a Midbar?
Radak (11): It has no settlement or building, so its length and width are seen more.
What is "Midbar Kadesh"?
Rashi (from Shabbos 89a): Midbar Sinai has five names. The others are Midbar Tzin, Midbar Kadesh Midbar Kedmus, Midbar Paran. It is called Kadesh, because Yisrael were Niskadshu (sanctified) there 1 .
Radak (11): It is a great Midbar - "ha'Midbar ha'Gadol veha'Nora ha'Hu", "va'Teshvu v'Kadesh Yamim Rabim" (Devarim 1:19, 46).
89a: It is called Tzin, because Yisrael were Nitztavu (commanded) there. It (Maharsha - Arvos Mo'av) is called Kedmus, because Kedumah (the Torah, which was already given at Sinai) was given [again] there. It is called Paran, because Yisrael reproduced there (every wife became pregnant with a boy after Matan Torah). It is called Sinai, for Sin'ah came to Nochrim due to it.
