1) Cornish surname 
Tregenna is a surname of Cornish origin. Recorded variations include Treganna, Tregona, Tregannah, Tregunna, Tregensoe, Tregensowe, Tregenza, and Tregenzo. The name is believed to have originated in the phrase tre-cenue (also tre-gonyow or tre-kensa), meaning the first or foremost farm or homestead on the downs. Examples from the church registers ...