Not knowing if some words were actual words that we use

I was working at school preparing worksheets for the students that I work with in my word study group. I was unsure of some words, so I used a dictionary. An example of these words is: brang and brung which weren't words. I had to look these words up in the dictionary to be sure. I have no idea why I didn't know that these weren't words. Another example of these words is ping, pang and hung were actual words and I had to look these words up in the dictionary to be sure.