From Tolkien Gateway

This definition doesn't seem to make sense. When Isildur uses the term "senya" in The Disaster of the Gladden Fields, it is a reply to the term "Atarinya", meaning "my father", which suggests that "senya" in this context means "my son". WadCheber 05:27, 9 July 2015 (UTC)

See also this page on the website University of Arda: WadCheber 05:30, 9 July 2015 (UTC)