I searched on a subscription site for Tomell baptismal records and found no records. I did find one marriage record in 1851 in Mullingar for a Elizabeth Tomell. No Tomell records on the Griffiths Valuation of 1853 for Co. Westmeath. No Tomell records in the 1901 and 1911 censuses anywhere in Ireland.
Likely Farrell is the correct name.
Roger McDonnell