From The Grammarly Blog:
You might not be familiar with the term portmanteau, but you likely use portmanteaus in your vocabulary and writing more than you realize.
A portmanteau (pronounced port-MAN-toe) is a word made by blending at least two words. The new word combines both the sounds and meanings of the originals.
To form a portmanteau, usually the first segment of one word is attached to the final segment of another word. Some portmanteau words are blended in other ways, like combining the initial segments of both words.
Why is it called a portmanteau?
Author Lewis Carroll describes the idea of portmanteaus in his book Through the Looking-Glass:
“Well, ‘SLITHY’ means ‘lithe and slimy.’ ‘Lithe’ is the same as ‘active.’ You see it’s like a portmanteau—there are two meanings packed up into one word.”
The word portmanteau itself is an appropriate embodiment of this word form, since portmanteau, which is French for porte (“to carry”) + manteau (“cloak”), describes a suitcase that opens in two halves. Portmanteaus “carry” both meanings of their word pairs.
Link to the rest at The Grammarly Blog