hypocorism

In Late Latin and Greek, the words hypocorisma and hypokorisma had the same meaning as hypocorism does in English today. They in turn evolved from the Greek verb hypokorizesthai ("to call by pet names"), which itself comes from korizesthai ("to caress"). Hypocorism joined the English language in the mid-19th century and was once briefly a buzzword among linguists, who used it rather broadly to mean "adult baby talk"—that is, the altered speech adults use when supposedly imitating babies. Once the baby talk issue faded, hypocorism settled back into being just a fancy word for a pet name. Pet names can be diminutives like "Johnny" for "John," endearing terms such as "honey-bunch," or, yes, names from baby talk, like "Nana" for "Grandma."