"Klingon warriors are passionate."
Translation:nong tlhIngan SuvwI'pu'.
Because tlhIngan is a noun in Klingon, not an adjective.
noun–noun compounds have the modifier first, then the modified (e.g. a QeD paq is a "science book" rather than being "book science").
noun–adjective phrases have the modifier second.
So Klingon is not strictly head-initial nor head-final; it depends on the type of unit.
And the fact that Klingon grammar is different than English grammar makes it even harder. Klingon doesn't even have adjectives - which is part of what confused brjaga. Most adjectives are actually verbs in Klingon and switch places depending on whether you are using them as a statement "warriors are passionate" or whether you are using them as a modifier "passionate warriors" (notice the English switches them, too, but English uses the opposite order from Klingon and adds an extra word into the statement).
However, some adjectives are actually nouns (this is true in English too - like "metal sword" or "Klingon warrior"). When an adjectival verb is used to modify a noun it goes after the noun in Klingon (in English, both types of adjectives go in front of the noun they modify). In Klingon when a noun is used to modify another noun in an adjectival manner, it goes before the noun it is modifying (this time it is just like English, which is part of why you can't just translate everything in reverse).
The grammar of Klingon is actually very simple and clear-cut, but it is very different than English, so can be confusing for those who don't have experience learning other languages. We're here to help any time you need it!