Fapropos: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/Fapropos - from package: ferret-vis

You may install the required package with command apt-get install {package}
Error in other languages:
Fapropos: bevel nie gevind nie
Fapropos: comandă negăsită
Fapropos: comando não encontrado
Fapropos: commande introuvable
Fapropos: command not found
Fapropos: käsku ei ole
Fapropos: không tìm thấy lệnh
Fapropos: komanda nerasta
Fapropos: Kommando nicht gefunden.
Fapropos: kommandot finns inte
Fapropos: komut yok
Fapropos: nie znaleziono polecenia
Fapropos: níor aimsíodh an t-ordú
Fapropos: no se encontró la orden
Fapropos: no s'ha trobat l'ordre
Fapropos: opdracht niet gevonden
Fapropos: parancs nem található
Fapropos: perintah tidak ditemukan
Fapropos: príkaz nenájdený
Fapropos: příkaz nenalezen
Fapropos: команда не найдена
Fapropos: командата не е открита
Fapropos: 命令找不到
Fapropos: コマンドが見つかりません