What is the word origin of smog?

The word "smog" is a portmanteau, meaning it's a combination of two words: smoke and fog.

It was first coined in 1905 by Dr. Henry Antoine Des Voeux, a British physician, to describe the dense mixture of smoke and fog that frequently blanketed London during the early 20th century.

This "pea-souper" fog, as it was often called, was a major public health concern due to its high levels of pollutants.