Since you're from Germany, I decided to get creative and have some fun! After some research and remembering waayyy back to high-school European history and general knowledge I have come to a conclusion!
:Warning: :Learning Is Taking Place Here:
(retrospective: wow I put too much effort into this, but man it was fun!! :D)
(retrospective #2: I can't believe I just wrote a 1 1/2 page paper on a Pokemon nickname...)
Ahem... As far as I can tell, modern-day Germany's ancient religious ties lay in Rome as geographic Germany was "encouraged" to enter the Roman empire (at the time "evangelical" Rome, but Christianity's names have become quite stereotypical (I'm Christian by the way, so I'm not hatin'), so we'll head back to the ancient Roman Pantheon of Gods. Now the main earth diety is "Tellus" or "Terra mater" (Mother Earth/Nature). That has two problems: 1. Landorus is male and "Terra Mater" is female. 2. wow is that name by itself is cliche. Back to the drawing-board
Okay, now before geographic Germany was taken in by the Romans, it belonged to a wide range of people-groups melded across northern Europe called the "Germanic people" (whose culture was basically thrown away except for, like, Beowulf which is really stretching it on the Germanic stuff). Germanic Culture's most recognizable religions is "Old Norse" (Exactly what you're thinking). Now, Thor is the personification of the Earth and harvest (literally landorus), but that seems more fitting for Thunderous since the main association with Thor is thunder (thanks Chris Hemsworth). Let's Dig Deeper!
(btw the "Old Norse" gods were adopted with name changes into the Roman Pantheon sorta like the Greek gods were so Thor sorta = Hercules... food for thought)
However, if we look around Thor, we can get some answers, like his mom, Jörð. If we wan't a male name, we have to shift around a bit. An alternate name for "Jord" is Fjörgyn. Finally, the answer approaches!! Fjörgyn also has a male counterpart "Fjörgynn, god of Earth " !! my final nickname is a culturally, historically, gender identity-ly (?) correct name, Fjörgynn !!!
Name analysis: as a plus, Fjorg is an Icelandic word meaning to animate or bring life (agriculture, anyone??) with gynn sounding like "Jinn" as in "Genie" as in the name of the trio it leads, fitting it into the theme Pokemon was going for here, perfect!!!
(Yes I know Demeter is the god that the german name for landorus was based off of, but its not relevant to Germany as demeter is a greek female harvest god and German influence that's what I'm kind of going for here to match Nelson Tangela's homeland...)
TL;DR: okay, so Germany, right? so like Germanic, right? so like Norse, right? So like Thor, right? But Thor is electric tho? So like Thor's mom, right? But, a guy tho, right? so that name, right? --> Fjörgynn <-- what the german name of landorus should have been in the first place since it represents German culture, and themes of Earth and agriculture, sounds like "jinn" so it has the Pokemon-brand pun in it, etc. ad infinitum!!
TL;DR: TL;DR: Um, why do I remember obscure facts about Norse mythology that I learned in the 10th grade for 3 seconds that merit half an hour of research to back
Or just call it "It's Fine" as in "It's fine, I got the Randorosu"
:Learning Warning Now Over:
(sorry for the wall of text, but I hope you like the name) :) or the alternate name ;)
