means The scientific study of language—its sounds, structures, meanings, and how it changes and varies across speakers and time.

from From Latin lingua, "tongue" (which also meant "language"), via French linguistique. The same lingua gives us "language," "linguine" (little tongues of pasta), and "bilingual." The "-istics" tail marks it as a field of systematic study, like "statistics" or "mathematics." The word for the discipline is a relatively modern coinage, arriving in English in the 19th century as the study of language matured into a proper science.