While I was having a chi-chat with my American colleague yesterday, we talked about some English sayings with the word "Tongue". She clarified some of my confusions, like
TONGUE TIED- It means that you know what you want to say, but you just can't say it clearly. Like can't find the right way or words to say it.
BITE MY TONGUE- It means that you wanted to say something, but you didn't say it. Like I wanted to tell my friend some bad news, but I didn't say it when I actually met her. I would say, "I bit my tongue."
PUT MY FOOT IN MY MOUTH- Ok, this has nothing to do with tongue, but it's an expression when I said something which I shouldn't have. Then I would say, "I wanted to put my foot in my mouth."
Interesting, huh? :)