a stranger to (someone or something)
1. Literally, someone who has never met someone or been to some place. I was a complete stranger to this country four years ago, but now I feel like I've lived here forever. I have heard her name mentioned by others, but she is a stranger to me.
2. By extension, someone who experience or knowledge of something. Often used in negative constructions. They brought in lawyer who was no stranger to such complex cases. He was a complete stranger to illicit drugs until he was well into his 30s.
stranger to (something or some place)
someone who is new to an area or place. Although John was a stranger to big cities, he enjoyed visiting New York. You are a stranger to our town, and I hope you feel welcome.