This word is not compatible with the name
Lalaith “Laughter” attested in
The Silmarillion. The most likely explanation of this name is that it is the unattested verb *
lala- “laugh” with the abstract noun suffix
-th seen in
tirith “watch(ing)” and
sirith “flowing”. This indicates a primitive form ✶
lala- instead of ✶
glada- (both primitives produce Quenya
lala-). If you were to accept
gladh- as the Sindarin word for “laugh”, then the word for “laughter” would perhaps be the equivalent abstract noun *
gladhath, and the name
Lalaith might be a mix of Quenya and Sindarin. @@@ Neo-Sindarin uses