-uva is a Quenya future tense ending.
A final -a drops out before the ending -uva is added; quanta- "fill", future tense quantuva "shall fill".
Example
- laituvalmet = "we shall bless them"[1]
- tiruvantes = “they will guard it”
- enquantuva = "shall refill"
- cenuva = "Shall see"[2]
References