From Tolkien Gateway

Soron (archaic þoron) means "eagle" in Quenya.[1] The form soron may only be the form of this word used in compounds. As an independent word, Tolkien wrote it as sorno in a letter from 1972.[2] Earlier, in the Etymologies of the 1930s, soron "eagle" appeared beside an alternate form sorne, but its plural form sorni ("eagles") indicated that sorne was the common form.[3]




This word derives from the primitive þoronō[2] from the root THORON "eagle", an extension of the root THOR "come swooping down".[3] In the development of Quenya words from Common Eldarin, a short vowel that follows another vowel of the same quality was lost[2], so that primitive þoronō developed into þorno and then sorno.