1. Yāmā. A class of Devas, mentioned in lists of devas between those of Tāvatimsa and those of Tusita
(E.g., Vin.i.12, A.i.228; iii.287; M.ii.194; iii.100, etc.).
Two hundred years of human life are but one day to the Yāma devā, and two thousand Years, composed of such days, form their life period (A.i.213; iv.253). Sirimā, sister of Jīvaka, was born after death in the Yāma world and became the wife of Suyāma, king of Yāmabhavana. From there she visited the Buddha with five hundred others. SNA i.244f.; see also VvA.246 for an upāsaka born in the Yāma-world.
In the Hatthipāla Jātaka (J.iv.475) mention is made of four Yāma-devas who were reborn as men.
The meaning of Yāmā is explained in the Commentaries (E.g., VibhA.519; PSA.441) as "those that have attained divine bliss" (dibbam sukham yātā payātā sampattā ti Yāmā). Other explanations are “misery freed" or "governing gods”. Compendium, p.138, n.2.
2. Yāmā. In some contexts, Yāmā seems to have been derived from Yama, king of the underworld - e.g in such expressions as "Yāmato yāva Akanittham" (From the underworld to the highest heaven). KhA.166.