Greetings from Proto-Indo-Europe
Ceci n'est pas un PIE
Whenever we look at the etymology of an English word, we find some PIE (Proto-Indo-European) root with an asterisk(*) next to it.
What's that all about?
First, the reason for the asterisk: PIE is only hypothetical. There are no written records of the language itself. PIE has been reconstructed from evidence found in related languages, but there's no Rosetta Stonefor PIE. The asterisk reminds us that every PIE root we think we know could be wrong.
Reconstructing PIE took place mainly in the 1800s, but had its beginnings much earlier. In 1585, a Florentine merchant named Filippo Sassetti noticed similarities between Italian and Sanskrit. In 1647, Dutch linguist Marcus Zuerius van Boxhorn proposed a common origin among Indo-European languages. But the real beginning of the study of Indo-European languages was in 1833, when German linguist Franz Bopp introduced his theory of Comparative Grammar.
During much of the 19th century, linguistic study was devoted in large part to reconstructing PIE. Careful comparisons and deductions have given us a confident result; PIE is the most completely and accurately reconstructed of all proto-languages.
The speakers of PIE, who lived between 4500 and 2500 BCE, are thought to have been a widely dispersed agricultural people who domesticated animals and had a strong tradition of oral history through heroic poems.
PIE is the ancestor of Latin, Proto-Germanic, Proto-Balto-Slavic, Proto-Celtic, Albanian, Greek, and Armenian—meaning that it's the great-grandparent of languages from Spanish to Polish to English to Welsh and many more.
That's why PIE seems to show up in so many etymological explorations—and why there's an asterisk next to every PIE root.
From Latin asteriscus, from Greek asteriskos, diminutive of aster (star) from—you guessed it—PIE root *ster- (also meaning star).
See Rosetta Stone on Wikipedia.
If you want to see what PIE might have been like as a language, see Schleicher's Fable.