Terrance "Terry" Cassidy, 78, of Merrimack, NH, passed away peacefully on February 21, 2026, after a long and courageous battle with kidney disease.

Born in Calgary, Alberta, Canada, on St. Patrick's Day (March 17), 1947, Terry was the eldest of Joseph and Carol (Smith) Cassidy's five children. He remained in his hometown after high school to pursue a degree in Engineering from the University of Calgary.

While working for the Canadian Department of Agriculture in the 1970s, Terry put his engineering, computing, and math skills to work as a true trailblazer. He achieved a feat that was entirely unprecedented: building the very first network to connect the department's research stations across Canada

Upon moving to New Hampshire in 1980, he worked for many years as a senior software engineer for Digital Equipment Corporation (DEC) before sharing his know-how as a consultant for the rest of his career.

Though generally a quieter man, Terry had a wicked sense of humor. He would often wait for the perfect moment to smirk and deliver a brilliantly witty retort. But he also wasn't afraid to be a goofball if the joke required it. He passed his love of comedy down to his children over countless hours spent watching Monty Python, The Marx Brothers, and The Simpsons together.

A lifelong learner, Terry was fascinated by genealogy and researching his family tree. He was a puzzle solver who applied his engineering mindset and love of mathematics to every hobby, from brainteasers to household projects. Terry loved spending time with his family, particularly when they were all together playing card games late into the night.

Terry is survived by his loving wife of 44 years, Shirley Fisher; his two daughters, Katelyn Cassidy (Jason Schuster) and Morgan Cassidy; his two grandchildren, Beckett and Sadie Schuster; his brother, Michael Cassidy (Linda Cassidy); and his three sisters, Denise Cassidy, Jo-Anne Grier (Michael Grier), and Kim Vanderstam (Dick Vanderstam).

Terry was predeceased by his parents and a much-loved member of the Cassidy Clan, Denise's partner Christopher Taggart.

Per the family's request, services will be held privately at a later date. In the meantime, St. Patrick's Day is right around the corner. Please consider raising a Rusty Nail or a mug of green beer in his honor.