trental
A set of 30 requiem masses, said once a day for a month or all in one day.
Trentals seyde he, deliueren fro penaunce Hir freendes soules.
The payment for this service.
Where it comes from
From Medieval Latin trentāle directly or via Old French trentel, from the neuter substantive of *Vulgar Latin trenta + -ālis (“-al: forming adjectives”), from Latin trīgintā (“thirty”).
Adapted from the Wiktionary entry trental (CC BY-SA 4.0).