Aldudénië (Q, possibly pron. [ˌalduˈdeːni.e]) is a poem lamenting the death of the Two Trees, composed by Elemmírë of the Vanyar, soon after the event. It was famous to all the Eldar, but never recorded.
The other element *dénie which obviously means "lament", is of problematic etymology since the intermedial "d" does not exist in Quenya (only the "ld" "nd" and "rd" are present). It might be some idiom of the Vanyarin dialect of Quenya.