I think OP was asking what it means as in how it came to haventhe meaning you describe. “You are welcome” seems to be a completely arbitrary thing to say and out of context.
Other commenters here explained it’s supposed to mean “you are welcome to my assistance” basically - which makes sense, but in the short form it makes little sense if you arenot familiar with the origins of the phrase (as I was until now)
I think OP was asking what it means as in how it came to haventhe meaning you describe. “You are welcome” seems to be a completely arbitrary thing to say and out of context.
Other commenters here explained it’s supposed to mean “you are welcome to my assistance” basically - which makes sense, but in the short form it makes little sense if you arenot familiar with the origins of the phrase (as I was until now)