Headcanon that when the Falconers need a quick one-syllable word to refer to Jack, but don’t want to use that name, they call him “Nerd”.
(I have a friend whose military callsign as a pilot is “Nerd”. RCAF personal callsigns are undignified things given you by other pilots, ideally a diminutive of your surname or referencing something embarrassing you did once, and when they get downtime they always see her reading thick history books for fun. So. “Nerd.” And this isn’t the first time I’ve been struck by how similar Canadian Armed Forces culture is to hockey culture.)
It happens organically. “What’cha reading, nerd?” and “Enjoy your computer date, nerd.” Pretty soon it’s not an epithet, it’s a name. “Nerd! Heads up!” and “Nerd, I’m open!” and “There ya go, Nerd!” It’s who he is to them. “Can’t read that? Get Nerd to do it, he has an Ivy League education.” “Nerd, why the fuck isn’t Toronto the capital?” “When did Orr’s record get beat? Where’s Nerd, he would know.”
Jack loves it. All his life, he was The Jock. Now he’s carved out an identity for himself that’s something entirely different.