To be consistent with other places in pandas (eg hdf uses 'index/level_0/1' I think, and I am now following the names that are given in `reset_index`). As far as I know this is the only place where `pandas_index` is used. It is also new (in 0.13 writing the index was not included in to_sql), so not really changing the behaviour for the user. See also https://github.com/pydata/pandas/pull/6642#issuecomment-37738409 for some discussion.