I have been looking for the term used for expressions such as "Now we're cooking with gas" for a while and even google couldn't answer it.
The phrase "now you're cooking with gas" originates in Britain in the 1930s when gas companies paid popular radio shows to use the phrase with the meaning "you're on the right track."
The phrase continued in to the television advertising era:
And has become part of the popular British English lexicon.
It is an example of quiet marketing to sell gas stoves.