Complex sentence: Both derive from a character named Myles-na-Coppaleen in Dion Boucicault's 1860 play "The Colleen Bawn", which, in turn, comes from the Irish "na gcapaillín", "of the little horses".
Split into simpler sentences: Both derive from a character named Myles-na-Coppaleen in Dion Boucicault's 1860 play "The Colleen Bawn". This, in turn, comes from the Irish "na gcapaillín", "of the little horses".