A friend of mine was putting this image in her Facebook profile. I didn't get it at first. Well, I could tell it's a vagina for sure, and it was obvious that it has something to do with women rights, but, what is that grass underneath? Why the yellow background? And what's motto!? After some search, I discovered that it is a play on the Gadsden flag, a flag that was used during the American revolution. In the original flag, it is a rattlesnake snake rather than a vagine, and the snake seems to be provoked, and is striking. Hence the warning; Don't Tread On Me (or I will strike). So, now it is clear.
A dictionary is enough to tell you that the world "tread" has nothing to do with "trade". Treading is some synonym of walking, hence the "treadmill" and W.B. Yeats' verse, "I have spread my dreams under your feet; Tread softly because you tread on my dreams”. But a dictionary is not enough to reveal the essential cultural background one needs to understand things people from other countries say.
I can write a sentence in perfect English, that no one can understand but an Egyptian here: "Mr. X has no end". An English speaking person will sure understand the sentence as sequence of words, but he will not understand what I mean by it, since he probably hasn't seen the Egyptian film the sentence was used it. If I say that someone is in Switzerland now, most of you will think of that European country whose flag is red with a white cross in the middle. But only an Egyptian will think of that one being in jail instead.
That's people who claim to be multilingual confuse me. For me, it is hard to speak more than two or three languages, it is even harder to understand the cultures of those languages as well. And not knowing that culture makes it even harder to claim that you speak that language fluently.