The native spelling is . However, Humans tend to have trouble writing
pIqaD symbols, so they've come up with various romanization systems.
The most widely accepted is that which is used by Marc Okrand, in which the planet's name is spelled
Qo'noS (note that this spelling is case-sensitive; it's never spelling Qo'nos or Qo'NoS). It is perhaps etymologically connected to the word
qo', which means "world". A common way of referring to the planet is
juHqo', meaning "the homeworld".
In
The Klingon Dictionary, Okrand uses
Kronos when writing in English and
Qo'noS when writing in romanized Klingon.
In
klingonaase, the planet is called
Klinzhai. This is not particularly strange: English-speakers call the Human homeworld
Earth (or
Terra). German-speakers call it
die Erde, French-speakers call it
la Terre and Swedish-speakers call it
jorden (or, when they're feeling fancy,
Tellus). Speakers of Mandarin, Japanese and Korean may all spell its name 地球, but the pronunciation varies from language to language.
Those all mean the same thing in their respective languages, but there are also languages in which the names are completely different. For example, the Navajo name
nahasdzáán means "our mother", the Ainu アィヌモシㇼ means "the land of the people", and the Scottish Gaelic
cruinne-cè means something like "the globe of the world".
Presumably, the Klingon homeworld would have had different names in different languages, and probably a number of variants variants in each language, too.