In Harry Potter and the Deathly Hallows Part 2 (2011), Griphook speaking to Harry Potter about Gryffindor:
Griphook: Only a goblin would recognize that this is the true sword of Gryffindor.
Hermoine: Who is the acquaintance?
Griphook: A Hogwarts professor. As I understand it, he's now headmaster.
What does "acquaintance" mean in this context?