The story
In 1856, Michael Henry Gill, printer for Dublin University, purchased the publishing and bookselling business of James McGlashan, and the company was renamed McGlashan & Gill. In 1875, it was renamed M.H. Gill & Son. In 1968, the company became associated with the London based Macmillan Publishers (founded 1843) and Gill & Macmillan was established. In 2013, the Gill family bought out Macmillan.
From Wikipedia’s article on Gill (publisher), shared under CC BY-SA 4.0.4