Every month we make a bracha on the new moon. In many siddurim where the bracha and nusach is featured it's called "Kiddush Lavana". If one looks in the poskim (See Rema Orach Chaim SIman 426 Sif 1, 2, 4) it's also written "kiddush levana (See also Shaarei Teshuva Siman 692 Sif-Katan 2 and Mishnah Brurah Siman 100 Sif-Katan 2 and other poskim and seforim including the Shelah) that write "kiddush lavana".)
What "kiddush" (or "sancitification") are we making on the moon? The nusach of the bracha (according to the Gemara in Sanhedrin Daf 42) is "m'chadash chadashim" as it appears in the siddur as well. We are making a bracha that which HaShem gives us a new moon each month. "M'chadash" (makes new) "chadashim" (the months or another word that used to refer to the moon.)
What "kiddush" is happening? Why is that loshon used in the poskim, seforim, and siddurim?