A portmanteau is a word made by blending parts of two other words. English creates them all the time, but only some survive. The successful ones usually feel clear, short, and easy to pronounce, so people adopt them quickly.
Several famous examples now seem completely ordinary. Smog blends smoke and fog. Brunch combines breakfast and lunch. Motel comes from motor and hotel. Mockumentary joins mock and documentary for a fictional film or show presented in a documentary style.
- We skipped breakfast and met for brunch at noon.
- The city was covered in smog after the heat wave.
These words worked because each one names something people needed to talk about, and each blend still hints at its source words. Even when speakers do not consciously notice the parts anymore, the meaning remains easy to grasp. That is why the best portmanteaus stop feeling like wordplay and start feeling like normal vocabulary.