What is the origin of butyraceous?

The adjective butyraceous is an expensive word for buttery. Butyraceous comes from Latin butyrum (both the first u and the y may be long or short), from Greek boútȳron “butter,” literally “cow cheese,” according to the traditional (and ancient) etymology, from Greek boûs (inflectional stem boo-, bou-) “cow” and tȳrós “cheese.” Both boûs and tȳrós are very ancient: both occur on Late Bronze Age Linear B clay tablets from Pylos (in the southwest Peloponnesus), and both words are of Proto-Indo-European origin. The closest non-Greek relative to tȳrós is in the ancient Iranian languages: in Avestan (the language of the Zoroastrian scriptures), tūiri– means “whey, cheeselike milk” and tūiriia– means “curdled (milk).” Herodotus states that butter was used by the Scythians, ancient Iranian nomads of the Russian steppes. Latin butyrum (with its variant būtūrum) becomes burre in Old French (beurre in French) and burro in Italian. Latin butyrum was borrowed by the West Germanic languages (as usual, the details and date of the borrowing are disputed): Old English has butere (English butter); German has Butter, Dutch boter. Butyraceous entered English in the 17th century.