There were probably many reasons for this - perhaps when the speaking of Irish began to die out in many areas, but there also appear to have been strong socio-economic reasons for doing so also. Many Irish families strove to improve their economic standing in their localities. This process continued into the 1800s as Irish society became socially conservative in Victorian times. The process soon began to be reversed however, due to the Irish National Awakening in the nineteenth century as the Irish population became more nationalistic and re-discovered their Irish heritage with the Gaelic cultural revival.
The first signs of a change in Irish surnames began with the mass dropping of the O and Mc prefixes to many surnames, that as I have already mentioned in previous blogs began in Elizabethan times. In the late 1700s however, the process became much more pronounced with the adoption of English surnames to replace Gaelic ones. To give my own surname as an example, many McGettigan families in the late 1700s began to change their surname to Gettins. The process does not appear to have reached my own family, but it got quite close - the family of Patrick McGettigan the Roman Catholic bishop of Raphoe in the early 1800s, who lived quite close to my own relations had begun to call themselves Gettins by the time Patrick first began to study for the priesthood. By the time he became bishop of Raphoe however, he had re-adopted his Irish surname and began to refer to himself as a McGettigan again.
Many other Gaelic Irish families in Ulster did the same thing. The Tyrone surnames McCawell and O'Gormley often became Campbell and Grimes, while the fine Inishowen surname Ó Duibhdhíorma became O'Dermot and even Darby. Many McDonnells in Ulster also became Donaldsons, while elsewhere in Ireland, people of for example the O'Byrne and O'Beirne surnames became Burns.
There was also a process whereby some families with Gaelic Irish surnames adopted literal English translations of their names. To give some examples ths surname McGowan (son of the smith) often adopted the surname Smith, while Ó Gabhláin (from gabhal - a fork) often became Forkin or Forkan. Ó Maoltuile or Mac Maoltuile became Flood, while Ó Géarain could become Sharpe, Ó Maoildeirg - Reddinton or Reid, Ó Maolghaoithe - Wynne or Wyndham, and Ó Claimhín - Swords. There are many more examples.
This is a very brief summary of an important period in the history of Irish surnames and I for one am glad that the process of adopting English versions of fine Irish surnames was halted and often reveresed by many Irish families during the nineteenth century.