-da suffix used to derive nouns denoting the result of an action, like yulda "draught, the amount drunk" (the stem YUL is here given the meaning "drink"). (PE17:68) Cf. also carda "deed" (q.v.) vs. the verb car- "do".
Quenya
yulda
draught, something drunk, a drink, the amount drunk
-da
draught, the amount drunk
suhto
draught
suhto noun "draught" (SUK)
yulma
cup
yulma (1) noun "cup" (Nam, RGEO:67), "drinking-vessel" (WJ:416, PE17:180). The plural form yulmar is attested (VT48:11). Yulmaya ("k") colloquial Quenya for "his cup" (the formally correct form being *yulmarya) (VT49:17)
yulda noun "draught, something drunk, a drink, the amount drunk", pl. yuldar (Nam, PE17:63, 68, RGEO:66). See -da regarding etymology.