Complex sentence: Until the end of the 18th century, Liam was virtually unknown outside Ireland, but in the mid- 1850s, over a million and a half people left Ireland to escape the catastrophic great famine, and from then on, Irish names were heard everywhere.
Split into simpler sentences: Until the end of the 18th century, Liam was virtually unknown outside Ireland. In the mid- 1850s, over a million and a half people left Ireland to escape the catastrophic great famine and, from then on, Irish names were heard everywhere.