The surname Sheddy is believed to have originated from the British Isles, specifically from Ireland. The name appears to have Gaelic roots, derived from the Irish surname "O Seadhaigh." This name has roots in the Gaelic "O'Siodhach," where "O" signifies "descendant of" and "Siodhach" means "peaceful" or "hospitable." The anglicization of Gaelic names often led to variations in spelling, resulting in the surname Sheddy.

Historical references to the surname Sheddy are relatively sparse, but it can occasionally be found in medieval Irish annals and records from the late Middle Ages. The surname first appears in written form in the 14th century, with early instances of the name noted in ecclesiastical and land records. For example, a Manus Sheddy is mentioned in an Irish manuscript from 1375 as a landholder in County Meath. Names at this time were often recorded phonetically, leading to different spellings such as Sheady or Shedde.

The earliest recorded example of the name Sheddy in British records comes from the late 15th century, when a John Sheddy was documented in parish registers in County Kildare, Ireland, around 1492. During the 16th and 17th centuries, the Sheddy name appears in a variety of legal and tax records as the English administration intensified record-keeping in Ireland. A notable mention is Thomas Sheddy, who was listed as a tenant farmer in Galway in 1623.

Another prominent individual bearing the name was Patrick Sheddy, a merchant from Dublin, born in 1685. He became known for his involvement in the wool trade, which was a significant industry in Ireland during the 17th and 18th centuries. Patrick's descendants continued to hold the surname in various forms, contributing to its persistence over the centuries.

In the 18th century, Bridget Sheddy, born in 1734, was a recognized midwife in County Mayo, Ireland. Her contributions to local communities and her skill in midwifery were well-documented in local records and oral histories. Bridget's prominence in her local community is a testament to how the name persisted across generations and regions in Ireland.

By the 19th century, the Sheddy name had spread to other parts of the British Isles and even to North America. One such individual was James Sheddy, born in 1820, who emigrated to the United States in 1845 during the Irish Potato Famine. James settled in New York and became involved in the nascent labor movement, advocating for better working conditions for Irish immigrants.

The Sheddy surname, while not extremely common, has a rich and varied history rooted in the Gaelic traditions of Ireland. It has persisted through centuries of phonetic changes and migrations, leaving its mark in historical records and the legacy of those who bore it.