pydata/pandas — comment on commit 5505aa112f3f6ef3ab9845c4a46b6491befafda0
File: pandas/core/frame.py line 1825
By wesm:

This is wrong in several ways

1. if an Index is passed in, this nukes the existing name, thus potentially having side effects on other objects
2. if a Series with a name is passed in, that name should be used