Complex sentence: The name Quinquagesima originates from Latin "quinquagesimus" (fiftieth), referring to the fifty days before Easter Day using inclusive counting which counts both Sundays (normal counting would count only one of these).
Split into simpler sentences: The name Quinquagesima originates from Latin "quinquagesimus" (fiftieth). This is in reference to the fifty days before Easter Day using inclusive counting which counts both Sundays (normal counting would count only one of these).