pip3 Installation, Please
To install pip3, the Python 3-specific version of pip, under Cygwin:
$ python3 -m ensurepip
This assumes the python3 Cygwin package to have been installed, of course.
pip2 Installation, Please
To install both pip and pip2, the Python 2-specific versions of pip, under Cygwin:
$ python -m ensurepip
This assumes the python Cygwin package to have been installed, of course.