CAN Bus Nominal Impedance
You mean, why not  220 ,100 or 75 or 50 Ohms?
It was conveniently close to what some wire pair gave for impedance , based on ratios of conductor to insulator diameter for certain Ribbon wire, twisted pair etc.
I think 93 ohms was common at one time for low capacitance coax on arcnet or something like that. Ribbon cable was 120 ohms and many others, due to voltage rating and thus insulation to conductor ratio.  Thinner insulation with a lower gap between conductors is lower impedance so 120 Ohms is I recall the typical 60~70 pF/m  (est.) and 500 to 1000 nH/m (ballpark)  but \$Z_o=\sqrt{\frac{L}{C}}\$  so I'll let you work it out.