mks135 wrote in linguaphiles

S'il vous plaît

Can anyone explain to me what the French construction "S'il vous/te plaît" comes from? As we know that could literally mean "If you like this", but we use this in the meaning of "please". But why there is no special word to say "please"? What if I don't like this ("Il ne me plaît pas")?
For example the sitiation: a boss or a teacher give an order by saying "S'il vous plaît" in order to say this in a more polite way. But how can we give the orders that can't be not obeyed by saying literally "if you like this" without paying attention to the fact that the person we talk to doesn't want to do this at all, but he is obliged?
I hope I'm well understood.