“Why the surname ‘Galba’ was first assumed by a Sulpicius, and where it originated, must remain moot points. One suggestion is that after a tediously protracted siege of some Spanish town the Sulpicius in question set fire to it, using toches smeared with resin (galbanum). Another is that he resred to galbeum, a kind of poultice, during a long illness. Others are that he was very fat, the Gallic word for which is galba; or that, on the contrary, he was very slender – like the galba, a creature which breeds in oak trees.”

(Suetonius, The Twelve Caesars, “Galba” 3, p. 248 in the Robert Graves/Michael Grant translation.)