iogerman software package provides Traditional German orthography dictionary for ispell, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install iogerman
iogerman is installed in your system.
Make ensure the iogerman package were installed using the commands given below,
$ sudo dpkg-query -l | grep iogerman *
You will get with iogerman package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Text Processing |
| Package | iogerman |
| Version | 1:2-31 |
| Description | Traditional German orthography dictionary for ispell |
| Sub Section | Text |