A class plural suffix, identical to N. -ath (PE21/57). It is possible this suffix was also used as (and was perhaps inspired by) the Gnomish general plural suffix -th.
Quenya
quentasta
historical account
quentasta
noun. historical account
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
Middle Primitive Elvish
-asta
suffix. collective plural
Doriathrin
-ath
noun. collective plural
quentasta noun *"historical account", "any particular arrangement (by some author) of a series of records or evidences into a given historical account" (not History as such, which is quentalë). (VT39:16, VT48:19). May include the "group suffix" -asta.