Cannot do agg if dataframe has column "name"
#### Code Sample, a copy-pastable example if possible

```python
# Your code here
import pandas as pd

df = pd.DataFrame({"a": range(10)})
df.agg({"a": 'mean'}) # this line runs good

df["name"] = range(10)
df.agg({"a": 'mean'}) # now we have RuntimeError: maximum recursion depth exceeded
```
#### Problem description

If a dataframe has a column which is called "name", doing aggregation on the dataframe will cause RuntimeError.

##### But if the column is not called "name" but with some variant like "name0", "name_", it runs good.

```python
import pandas as pd

df = pd.DataFrame({"a": range(10)})
df.agg({"a": 'mean'}) # this line runs good

df["name_"] = range(10)  # not "name"
df.agg({"a": 'mean'}) # this line runs good as well
```

#### Expected Output

#### Output of ``pd.show_versions()``

<details>

[paste the output of ``pd.show_versions()`` here below this line]

INSTALLED VERSIONS
------------------
commit: None
python: 2.7.15.final.0
python-bits: 64
OS: Darwin
OS-release: 18.0.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: None.None

pandas: 0.23.4
pytest: None
pip: 18.1
setuptools: 40.6.3
Cython: None
numpy: 1.16.0
scipy: 1.2.0
pyarrow: 0.11.1
xarray: None
IPython: 5.8.0
sphinx: None
patsy: None
dateutil: 2.7.3
pytz: 2018.9
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: None
openpyxl: None
xlrd: 1.1.0
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: 0.9999999
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: 0.2.0
fastparquet: None
pandas_gbq: None
pandas_datareader: None

</details>
