A portmanteau, consisting of two words combined to create a new term, is a linguistic phenomenon that has been used for centuries. However, the word "portmantologism" is not very commonly used in the English language, and one can use synonyms for easier usage. "Blending" is a common synonym for the word, which refers to a new word created by combining two existing ones. "Mashup" refers to the concept of combining two different things or ideas to create something new. Another synonym for "portmantologism" is "neologism," which refers to any new word or phrase created independently or by using existing words. In short, there are many ways to describe the combination of words used to create a single, new word, and each has its own nuances and usage.