A verb appearing as hyarin “I cleave” in The Etymologies of the 1930s as a derivative of from the root ᴹ√SYAD “shear through, cleave” (Ety/SYAD). In the Outline of Phonetic Development (OP1) from around this time, Tolkien had an (unglossed) verbal stem hyar- also derived from ᴹ√SYAD, but in that document the root seems to mean “compact, compress”. However in the Quenya Verbal System from 1948, hyare again meant “cleave” (PE22/102). See the entry on √SYAD for further vacillations on the meaning of the root.

Conceptual Development: The Gnomish Lexicon of the 1910s had ᴱQ. hyanda- as the cognate of G. †hanna- “mow, cleave” (GL/48) likely based on the early root ᴱ√HYAŘA “plough through” [HYAÐA] (QL/41). Early Qenya Word-lists of the 1920s had ᴱQ. hyar- “plough”, probably form the same root (PE16/144).

Neo-Quenya: For purposes of Neo-Quenya, I would keep the sense “cleave” for the basic verb despite Tolkien’s vacillations on the meaning of the root. I think it could also retain its 1920s meaning “plough” = “*cleave the earth”.