Sick and tired of

How can someone be sick and tired of something when ''sick of'' and ''tired of'' mean the same thing? Isn't that like saying. I going to go eat dinner and supper? There's a policeman and police officer outside the house. Cows masticate and chew grass. All of those sentences make no sense. Why does ''sick and tired of'' make sense?

Being sick and being tired are two different things, Mike, however, they can be related. I can be sick of doing something (an expression that means an activity literally "sickens" me) and I it is possible to grow tired of doing something. Thus, I become "sick and tired." To be tired doesn't necessarily mean one is sick, but the two often go hand in hand. If I stayed up late and am tired, it doesn't mean I also have the flu.

I think you need to analyze a little bit more, Mike, before you make your statements about "things not making sense."

*EDITING: and it is possible for me to grow tired.....(omit that "I")

I know being sick and being tired are two different things. I'm not saying they're the same. But, ''sick of'' and ''tired of'' are often synonyms. For example this sentence ''I'm sick of the flu''. This can either mean ''I'm sick with the flu'' or I'm tired of having the flu''.

''Sick and tired of'' makes sense because people use it, but why? I'm going to have dinner and supper. Makes no sense.

Yes, the expressions are synonyms, but one must look at the root words to understand why.

"I'm tired of this."

"I'm sick of this."

"I'm sick and tired of this."

All of these sentences mean the same thing, but since the key words "sick" and "tired" mean different things, I don't find the expression "sick and tired" to be redundant.

I'm a learner but my guess is the first word (sick) is used as a filler for showing strong opinion.

The tautology is for emphasis, which is the only good reason to use tautology.