Incorrect spelling, explanation: show is an irregular English verb and its past participle form can be spelled as showed or shown. Unfortunately, these two forms are often mixed by many English users, which results in various spelling mistakes. One of them is to spell shown as showned, which is wrong.

Correct spelling, explanation: the base form of shown is to show, and shown is its past participle form. The word had already existed in Old English but in the form of sceawian, which could be translated as to look at or to inspect. Before shown started to look the way it looks in modern English, it was also influenced by Dutch and German languages.

Definition of show:
1. verb (the past participle form) – to be seen; to present how to do something; to express, e.g. emotions.
Our teacher has shown us a great movie about global warming in today’s Biology lesson.
The exam results are on the wall and I can see her face has shown bitter disappointment.
My dad has just shown me how to drive a car and I have no idea how I will handle that on my own.

Expressions and idioms with show:
A few popular expressions and idioms with shown are:
1. shown your face – to appear in a place where you aren’t expected because you did something wrong,
I couldn’t believe my eyes when he has simply shown his face as if nothing had happened.
2. shown someone the door – to make it obvious that you want someone to leave,
I’m crying because he has just shown me the door after I told him that I love him.
3. shown the flag – to show your support for the group you belong to,
He has truly shown the flag by taking part in every gathering of our club.