These names are mentioned only in passing by Audsley, with no definition, and citing only a single example (see Riga, below). The suffix bass is routinely used by German organ builders to indicate that a stop belongs to the pedal division. All the examples we know of are at 6-2/5' pitch. Thus, we can deduce that these names are used for a Grossterz in the pedal.

Terzbass 6-2/5', Pedal; Passau Cathedral, Passau, Bavaria, Germany; Steinmeyer 1924-28.

Terzbass 6-2/5', Pedal; Riga Cathedral, Latvia; Walcker 1883.

Terzbass 6-2/5', Pedal; Votivkirche, Vienna, Austria; Walcker 1878