Ladarius is a modern elaborated name, likely built from the La- prefix and Darius, meaning loosely "possessing goodness" by association.
Ladarius is an American original — a name born from creative synthesis rather than imported whole from an ancient language. It belongs to a robust tradition of African-American naming innovation, particularly prevalent in the American South, in which classical and historical names are elaborated with melodic prefixes and suffixes to create something new, personal, and sonically distinct. At its core sits Darius, a name of deep Persian antiquity: it derives from the Old Persian Dārayavauš, meaning "he who holds firm the good" or "possessor of good."
Three Persian kings named Darius — including Darius the Great, who built the Persian Empire to its greatest extent in the fifth century BCE — carried this name into the historical record with enormous weight. The prefix "La-" is one of the most generative in African-American naming tradition, appearing in names from LaShonda to LaRon to Lafayette, and functioning as an elegance-marker, a way of personalizing a root name and giving it a particular rhythm. Ladarius, then, is Darius dressed in American clothing — elevated, made singular, given a particular musicality that pure Darius does not possess.
It gained popularity in the 1980s and 1990s, when this style of inventive naming reached its creative peak. The name is most at home in the American South and has appeared on football fields and basketball courts, in classrooms and churches. It carries with it both the imperial legacy of ancient Persia and the living, creative energy of American Black naming culture — a combination that is richer for encompassing both.