S. initial [w] became [gw]; [w-] > [gw-]
At every conceptual stage of Sindarin (including Gnomish and Noldorin), an initial w- became gw-. An identical development took place in Welsh (WGCH/§100i). Tolkien described this change several times:
Since ON w became initially gw in Exhilic, x was normally employed as gw (Feanorian Alphabet, 1930s, PE22/32).
... for gw is only the S. initial form of basic w-: as wath “shadow”, initial form gwath, i-wath “the shadow”, a chwath “and a shadow” (notes on a “and” from the late 1950s or early 1960s, PE17/41).
There are numerous examples of this change. Here is a representative from each conceptual period:
- ᴱ√u̯iri [wiri] > G. gwir- “look (at)” (GL/46).
- ᴱ✶wikā > ᴱN. gweg “man, male” (PE13/162).
- ᴹ✶wingē > N. gwing “spindrift, flying spray” (Ety/WIG).
- ✶wanya > S. gwain “fair-haired” (PE17/150).
This sound change did not take place medially, and ended up playing a role in Sindarin’s mutation system. In particular, the soft-mutation of initial gw- was w-, not because the g was lost, but rather because it was prevented from forming in the first place.
Conceptual Development: It seems Tolkien adopted this sound change from Welsh very early and retained it through all conceptual stages of Sindarin. The only complication was that in the earliest stages, initial gw- could also be derived directly from primitive gw-, since unlike Sindarin and Noldorin a primitive [gw] did not become [b] in Gnomish.