“Firstling” isn’t a commonly used word now, but it appears in classic texts. There are several spots in the Bible’s Old Testament that mention firstlings, often referring to various animals’ offspring. And in the fourth act of “Macbeth,” the titular character says in an aside, “From this moment the very firstlings of my heart shall be the firstlings of my hand,” meaning his initial thoughts will translate into his immediate actions. This word stems from the Old English “fyrest,” meaning “foremost.” The Old English “-ling” comes from the Proto-Germanic “-lingaz,” meaning “small, immature, miniature” or “follower.”