The full name of Lórien, loosely translated by Treebeard as “Dreamflower” (LotR/467), more accurately “Lórien of the Blossom” (RC/300). This name is a combination of loth “flower” with its shorter name Lórien (SA/loth, PE17/48). The translation “Dreamflower” alluded to the Quenya name that inspired it: Q. Lórien “✱Dream Lands” (PE17/48).
Conceptual Development: This name was already N. Lothlórien when it first appeared in Lord of the Rings drafts from the 1940s (TI/218). In his Words, Phrases and Passages from the Lord of the Rings (WPP) from the late 1950s or early 1960s, Tolkien indicated that the pure Sindarin form of the name would have been Lothlewerian(d), plural Lothlewerien(d), if it were derived from the sense “gold” as its Nandorin name Lórinand and it would have been Lothlýrian, plural Lothlúrien, if it were derived from the sense “dream” as the Quenya name Lórien (PE17/48).
The forest ruled by Galadriel, originally named in Nandorin Lórinand “Valley of Gold(en Light)” (UT/253) but adapted into Sindarin (LotR/1127) in imitation of Q. Lórien (UT/253), the realm of Irmo in Aman.
Possible Etymology: In English, it was often called the “Golden Wood” (LotR/337), so its initial element is likely a variant of the prefixal form glor- of glaur “gold” (without the “g” due to its Nandorin origin), while its final element could be the plural -ien “lands” of the suffix -ian(d), hence: “✱Golden Lands”.
Conceptual Development: In the Gnomish Lexicon from the 1910s, the Gnomish equivalent of ᴱQ. Lórien was G. Luriel >> Lûrien (GL/55) while in The Etymologies from the 1930s, its Noldorin equivalent was N. Lhuien (Ety/LOS). When the forest was first named in Lord of the Rings drafts from the 1940s it was Lórien (TI/234), which Tolkien indicated was a Lemberin name in drafts of the Lord of the Rings appendices (PM/36). The derivation given above was described in Tolkien’s later writings on the history of Galadriel (UT/253).