Complex sentence: The label "big hair" for such styles originated in the late 1970s, when these styles were beginning a period of popularity; the label has been applied to similar styles that have become fashionable at various periods in history.
Split into simpler sentences: The label "big hair" for such styles originated in the late 1970s, when these styles were beginning a period of popularity. Similar styles that have become fashionable at various periods in history.