The name Chassidy is a relatively modern name that first emerged in the late 20th century. It is believed to be a variant spelling of the name Cassidy, which has its origins in the Irish Gaelic language. The name Cassidy is derived from the Irish surname O'Caiside, which means "descendant of the curly-headed one."

While the name Chassidy itself does not have a long historical lineage, its roots can be traced back to ancient Ireland and the Celtic culture. The earliest recorded use of the name Cassidy dates back to the 16th century, when it was primarily used as a surname in Ireland.

One of the earliest known bearers of the name Cassidy was John Cassidy, an Irish soldier who fought in the Siege of Limerick in 1691 during the Williamite War in Ireland. Another notable figure was Sarah Cassidy, an Irish poet and writer who lived in the late 18th century and published a collection of poems titled "The Poetical Works of Sarah Cassidy" in 1797.

In the 19th century, the name Cassidy gained popularity among Irish immigrants in the United States. One of the most famous Americans with the name was Butch Cassidy, born Robert LeRoy Parker in 1866. He was a notorious train robber and outlaw who became a legend of the American Old West.

As the 20th century progressed, the name Cassidy became more widely used as a given name, particularly in the United States and Canada. One of the earliest notable figures with the first name Cassidy was Cassidy Petty, an American actress born in 1975 who appeared in various television shows and films.

Other notable individuals with the name Cassidy include Cassidy Hubbarth, an American sportscaster born in 1984, and Cassidy Janegan, a Canadian ice hockey player born in 1990. While these examples feature the more traditional spelling of Cassidy, the variant spelling of Chassidy emerged in the late 20th century, likely as a unique and personalized version of the name.