[HPsquared]

Staying with Physics, "Gb/S" is Gigabarns per Siemens. Some relation of electrical conductance with cross-sectional area.

The barn is a unit of cross-sectional area, based on the Uranium nucleus (area 1 barn). Uranium is pretty large in atomic terms; the name is from the idiom "couldn't hit the broad side of a barn".

[jagrsw]

And since 1/S = 1Ω, it'd be Gigabarnohm.

[robertlagrant]

Hence the old joke: how many Gigabarnohms does it take to start a circus?

Answer, of course, one million.