oiale is a a Quenya adverb meaning "forever, eternally, in eternity”. It can also be used as a noun for "everlasting [?age]"
The word could have be the Root OY or a stem like oio "an endless period" plus an ending -le.
 See also
- ↑ Parma Eldalamberon 17
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), The Lost Road and Other Writings, The Etymologies