Do you ever wonder how you have lived so long and not heard certain popular phrases? I had never heard "ho" used in its derogatory sense until I was in grad school, and I swear the people in my middle school and high school called each other every other insulting name ever invented. I thought it was a recent invention, but I learned from my mother that it was used back in her youth. "Junk" and "pacakge" are two other terms that I never picked up in school, in spite of the best efforts of my classmates to give me an education in sexual slang. Did I just never hear them, or are they relatively new? Or are they, perhaps, somewhat regional? I don't care about the words themselves, but it baffles me how I didn't learn them before adulthood.
On a more palatable note, I never heard the expression "over the top" used in the sense of "over the line" until I was 30. The first person I heard use it was Canadian, so I thought perhaps it was specific to that country, but I have heard it used by all kinds of Americans since then. The odd thing about this phrase is that it dates back to World War I, and it has a specific meaning: "over the top" was the command given to infantry when they had to come out of their trenches and attack the enemy. Because the war was so bloody and favoured the defense, going over the top was the last thing a soldier wanted to hear. I had heard it, but only rarely, used to mean an all-out offensive, with the connotation of a certain desperation -- risking one's soldiers in a desperate attempt to attain the objective. It's not at all the same thing as "over the line"; I can see how the meaning might migrate to that, but I think its use in that sense was probably the result of mixing up the two phrases.