“Dad?”
Ben squats at the edge of a hatch in the Millennium Falcon, watching his father fix the hyperdrive. The hyperdrive is in a constant state of either needing to be fixed, being fixed, or just about to break. At this stage, Ben isn’t aware that hyperdrives can work any other way.
“What?” Han Solo’s voice is muffled, followed by an arc of sparks and a hastily-cut-off swear word. This kind of thing is regular enough not really bother Ben, so he calmly repeats himself.
“Dad? Why am I called Ben?”
This finally gets Han’s attention: his dad pokes his head up through the hatch and blinks in the sudden light. “Your mom didn’t tell you?”
Ben shakes his head. Han makes a silent appeal to the sky- the roof of the Falcon, maybe, or something further above- then picks up a hydrospanner.
“Ben was the name of the guy who introduced me to your uncle Luke.” The rest is slightly distorted as Han ducks back into the guts of the Falcon, Ben leaning over to watch him as closely as he can. “Walked up to me in this place, Mos Eisely, ah, uh, well, it was kind of a bar and your old dad was there looking for work-”
“Smuggling.” Ben says with satisfaction, because the word always seems to embarrass his dad.
“Smuggling, yes, okay, and this old guy comes up to me, all dressed in robes. Says he needs a pilot.”
“And you were the best.” This is an undeniable fact, like mom being in charge or Uncle Chewis giving the greatest hugs. It just is, so Ben’s surprised when Han stands up again, putting the hydrospanner back and leaning against the side of the hatch.
“I don’t think I was, you know.” He points a finger at Ben. “Don’t tell anyone. But at the time? In that place? I’m sure there were better pilots, with less noticeable ships. But he chose me.”
“And then you met uncle Luke and mom and saved the galaxy.”
“Single-handed, yep.” Han reaches over and ruffles his son’s hair. “So the next time someone unexpected came and changed my life, I thought, I know what to call him.”