OS. [rl] became [ll]; [rl] > [ll]
It seems that [rl] > [ll] in older Sindarin compounds, as with OS. glawar-lin > S. Glewellin “Song of Gold” (PE17/61) and er + loth > S. elloth “single flower” (VT42/18). This was not true of later or reformed compounds, since rl could appear in later Sindarin: aerlinn, Dagorlad, Forlond, etc. Compare this to Quenya, where [rl] > [ll] was the regular sound change.
Conceptual Development: There are no signs of this phonetic development in Noldorin or Gnomish, but it could simply be lack of examples.
Phonetic Rule Elements
Phonetic Rule Examples
|glawarlinde > glawallinde||rl > ll||OS. †glawar-lin > S. Glewellin||✧ PE17/61|