Lockbearer is the name that Galadriel uses of Gimli in her message delivered by Gandalf in the Fangorn Forest. Galadriel had given three golden strands of her hair to Gimli as a farewell present in Lothlórien.
Gandalf says: '"To Gimli son of Glóin", she said, "give his Lady's greeting. Lockbearer, wherever thou goest my thought goes with thee. But have a care to lay thine axe to the right tree!"' (LoTR, Book II, Ch. 5).