My cat does this as well when a bird is close by.....they think they are going native with the lingo. Unless he is taking a course on the internet while I am out, my bird is just pretending to speak beak talk.
acorn - fruit of the oak tree: a smooth thin-walled nut in a woody cup-shaped base. acorn cup, cupule - cup-shaped structure of hardened bracts at the base of an acorn. oak tree, oak - a deciduous tree of the genus Quercus; has acorns and lobed leaves; great oaks grow from little acorns. fruit - the ripened reproductive body of a seed plant.
Acorns served an important role in early human history and were a source of food for many cultures around the world. For instance, the Ancient Greek lower classes and the Japanese (during the JÅmon period) would eat acorns, especially in times of famine. In ancient Iberia they were a staple food, according to Strabo.