Yes, I believe the French expression for this is double entendre.
It is like saying have a good day, only people replace day with one. It is a saying. Have a good one.
Saying one thing while meaning another is known as sarcasm. It involves using irony to convey a message that is usually opposite of what is stated, often with a humorous or mocking tone.
When someone uses a double negative they end up saying the opposite of what they wanted to and the meaning of the sentence doesn't get across to the other person.
Yes, that is the meaning of the slang.
Double entendre is French for double meaning of a word or a phrase - an apparent, innocuous, meaning and another, normally more mischievous, one. Often used by gossip writers and by politicos.
Saying that someone has "one foot in and one foot out" means that they are undecided or not fully committed.
You were probably referring to the saying "you can't have cake and eat it too" meaning one cannot have more than one deserves or can handle at one time.
double-entendre, calembour
meaning of double hump
The meaning of a double entendre in simple terms it is a figure of speech that describes one word with having two distinct and different meanings of their own.
one says 'thank you" in any civilized country for services rendered
The double star means Upgraded Grade by one level.