The fra'as guarded the farmlings with their krytoses: Calling It Bread
There is a school of thought that holds you should not conlang at all. Randall Munroe (xkcd.com) summarizes it admirably:
John Scalzi (Whatever) prompted some discussion of the issue—mainly in Neal Stephenson’s Anathem—with this comic. One commenter links it to a specific rule of Orson Scott Card’s: if it’s bread, call it bread. Here is the full quote:
Nothing is more tacky than to have a bunch of foreign-sounding words thrown into a story for no better reason than to have something that sounds foreign. James Blish called such needlessly coined words “shmeerps.” If it looks like a rabbit and acts like a rabbit, calling it a shmeerp doesn’t make it alien.
If mugubasala means “bread” then say bread! Only use the made-up stuff when it used for a concept for which there is no English word. If your viewpoint character thinks that mugubasala is nothing but bread, then later discovers that it is prepared through a special process that releases a drug from the native grain, and that drug turns out to be the source of the telepathic power that the natives are suspected of having, then you are fully justified in calling the bread mugubasala. It really is different, and deserves the added importance that a foreign name bestows. [How to Write Science Fiction & Fantasy, Orson Scott Card]
The accidental conlanger is advised not to take the time to invent a word for bread if it’s not mugubasala, but even if your (as yet unconstructed) language will have no untranslatable terms like mugubasala, there is still room to conlang. The most basic conlangs are naming languages.
Much further discussion of the cartoon appeared on October 9th on Language Log, mainly in the comments.