Hello poppyo,
The 1854 extracts of Griffith's Valuations of Offaly on John Hayes' website lists six people with the surname Sheerin but none in Daingean which was originally called Philipstown.
Thomas Sheerin, Gorteen, Geashill
Robert Sheerin, Main Street, Edenderry, Monasteroris
Thomas Sheerin, Ballinvally, Geashill
Patrick Sheerin, Gorteen, Geashill
Patrick Sheerin, Ballinvally, Geashill
Edward Sheerin, Cloncraff or Bloomhill, Clonmacnoise
Christopher