First found in county Tipperary, where they were seated from very ancient times, and were descended from the tribe of Uaithne.

In the 18th and 19th centuries, hundreds of thousands of Irish immigrants landed on North American shores. Although many of them were merely looking for a free plot of land and living of their very own, many later immigrants were desperately fleeing an overcrowded land that did not have sufficient food for its inhabitants. The exodus from Ireland was greatest during the 1840s when the Great Potato Famine had stricken the island. Although this large influx of Irish was unpopular with the great majority of people already established within the major centers, these Irish were critical to the speedy development of the United States and those colonies that would eventually become known as Canada. These immigrants provided the cheap labor required to build modern roads, bridges, canals, and railways. Research of passenger and immigration lists has shown a number of immigrants to North America baring the name of Leahy: Arthur Lahey settled in Virginia in 1649; Andrew, Dennis, James, Patrick Lahey all landed in Philadelphia, Pennsylvania between 1833 and 1868; James, Thomas, and William Lahey settled in Boston Massachusetts between 1848 and 1849.

Motto Translated: All comes from God.

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