ENH #15972 added margins_name parameter for crosstab
 -  closes #15972
 -  1 tests added / passed
 -  passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``
 -  whatsnew entry

ok I think you have a conflict on 0.21.0.txt (pls rebase again). # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16489?src=pr&el=h1) Report
> Merging [#16489](https://codecov.io/gh/pandas-dev/pandas/pull/16489?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e81f3cc30725443a1d36ec27279f3fec4eed60ec?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16489/graphs/tree.svg?height=150&src=pr&token=eZ4WkYLtcO&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/16489?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #16489   +/-   ##
=======================================
  Coverage   90.43%   90.43%           
=======================================
  Files         161      161           
  Lines       51045    51045           
=======================================
  Hits        46161    46161           
  Misses       4884     4884
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.27% <100%> (ø)` | :arrow_up: |
| #single | `40.16% <16.66%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16489?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/reshape/pivot.py](https://codecov.io/gh/pandas-dev/pandas/pull/16489?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9waXZvdC5weQ==) | `95.08% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16489?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16489?src=pr&el=footer). Last update [e81f3cc...b5756ef](https://codecov.io/gh/pandas-dev/pandas/pull/16489?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @jreback 
@TomAugspurger 

Thank you for your checking and helpful comments.
 Thanks @cmohl2013 !