Why was "Absolute Izhar" (Obviousness) given this name, and it is that the Idgham (Merging) comes in one word?

The esteemed questioner means by “idgham in one word” the pronunciation of the nun before the waw and ya, which is called Izhar Mutlaq (absolute clear pronunciation). The Izhar Mutlaq occurs in the Quran in four words: “Sinwan” (صنوان), “Qinwan” (قنوان), “Bunyan” (بنيان), and “Ad-Dunya” (الدنيا).