As an example, I was recently asked to explain the phrase “getting off at Redfern”. Now for those who may be unfamiliar, this is Australian slang for coitus interruptus. In that, Redfern is the last stop just before Sydney’s Central railway station.
Another example is “How’s your father?” For example, if someone asked you over to their house for a little bit of “how’s your father”, then you need to know that they may be asking you for more than a cuddle.
So as you can see, things like “slap and tickle” may or may not be what they seem. It’s best to ask an expert before committing to anything obscure.