You use oil to grease the motor of your car, but also to prepare a salad. In both cases, you should call it yoogh (իւղ) in Armenian. Indeed, yoogh also means “fat,” but this is not strange, since oils are basically liquid fat.
Both oil and yoogh have a distant ancestry. The Armenian word was borrowed from some long-lost Mediterranean language, which was also the source for Greek ἔλαιον (élaion) “olive oil” and ἔλαια (élaia) “olive tree,” and Latin oleum “oil.” Latin became the source for a variety of Latin and Germanic languages, including English oil. Incidentally, the Armenian word karyoogh (քարիւղ) is a literal translation of Latin petroleum (“stone oil”), the technical term for what we use to fill the tanks of our cars, e.g. “gas.”
Knowledgeable readers are also aware that there is a specialized term in Armenian, tzet (ձէթ), which designates olive oil. It already appeared in the Armenian translation of the Bible, probably borrowed from Syriac zaita. Tzet would become the root of many compound words, such as tzitabdoogh (ձիթապտուղ) “olive,” already present in the fifth century. In the same way, Arabic zait “olive oil” would become the source of Turkish zeytin “olive” much later.
Generally speaking, Armenian names for fruit trees have their origin in the name of the fruit, with the addition of the suffix –eni; for instance, khntzoreni (խնձորենի) “apple tree” or geraseni (կեռասենի) “cherry tree.” Some flower trees share this rule; for example, varteni (վարդենի) “rose tree.” The name of the olive tree is an exception. Its root was not the fruit, but the oil produced by the fruit. Thus, we have tziteni (ձիթենի), which literally means “olive oil tree.”
The names of oils derived from various fruits and plants are composed in the same way as in English; for instance, armavi yoogh (արմաւի իւղ) “palm oil.” However, the word tzet has given birth to a long-standing misuse in colloquial language. Apparently, many Armenian speakers (and dictionary writers, unfortunately) tend to think that tzet means “olive” and use the incorrect word tzitayoogh (ձիթաիւղ) as if it meant “olive oil.” It is funny, because if they gave it a thought, they would realize that they are actually saying... “oil oil.”
Conclusion: if you use olive oil, rely on tzet. For other oils, go to yoogh. Never trust tzitayoogh.