"Bridged Indexes" is a non-standard term. These are just secondary indexes using logical pointers with a mapping index. IIRC, Oracle, Hana, and HyPer do the same thing.
Source: https://db.cs.cmu.edu/papers/2017/p781-wu.pdf (see Table 1 + Section 6.1)
> secondary indexes using logical pointers with a mapping index.
rolls off the tongue.
It's more than just one mapping index, though.
The CMU paper indicates the logical keys are either TupleID or Primary Key, while the bridged index is actually a TupleID that resolves to a Primary Key, which resolves to the actual tuple - one more level than indicated by 6.1's explanation of logical pointers.