Thomas Henry Davidson (c1848-1911) was the uncle of my great grandfather William James McCann, (pictured here with his wife Mary Ann Taylor and his daughter, my grandmother Eliza McCann).
Thomas Henry Davidson was better known as Hammerhead and worked as a lighterman. Both the McCann and Taylor families had men who worked as lightermen. Hammerhead: a Glimpse into the Life of a Lighterman appeared in the 2020 edition of History Armagh p34-39 and can be viewed at History Armagh 2020
Links to family tree
William James McCann and family can be found here