Colloquialism~~is an expression not used in formal speech, it is a manner of speaking, or writing that is characteristic of familiar "common conversation". Wikipedia
Colloquialism~~a. expression. b. a local or regional dialect expression. Merriam-Webster Dictionary
Colloquialisms can be words such as: "ya'll," or "gonna". They can also be phrases such as: "ain't,"or "nothin". They can also be a full expression such as: "There is more than one way to skin a cat." Wikipedia
In the south there are many, many, of these "expressions".
"My stars and garters."
"Hotter than a six shooter."
"I'm gonna box your ears."
"I'm fixin to go to the store."
"What chew talkin bout."
I looked on two websites and found other regional "expressions". You can learn Hillbonics the dialect of southern West Virginia, examples are:
"Pull up a cheer,"
"Set a spell,"
"It's rainin like a big dog,"
"Iffen you peart off to me agin I'm goin' to wear you out."
In Yorkshire, England their "expressions" is called Yorkshire isms, and examples are:
"I've seen better-legs on-a table." (A woman who has ugly legs.)
"E's got a munkon." (He's a little upset.)
"O'Reyt." (Are you alright.)
"Get a benny on." (To get upset, or angry.)
I love to hear these "expressions" they continually make me laugh, I often wonder how in the world the saying originally got started, like did someone really try to skin a cat?