Sirius knows the word, of course. He'd heard it even before his arrival in this city though the things he'd imagined back home were a good deal larger than anything he's seen here in Darrow. And he still isn't entirely sure of their purpose regardless of size.

Instead of asking, however, he sits up and reaches to shake the boy's hand. "Sirius," he replies with a grin, letting go only to take another sip of his tea. "I've been under the assumption we all showed up here by magic. Not certain you can gauge such a thing on a Muggle contraption though. Are you having any luck?"