Quenya 

órava-

have mercy

órava- vb. "have mercy", followed by locative: "have mercy on". Órava (o)messë "have mercy on us" (VT44:12)

órava-

verb. *to have mercy

Element in

ócama-

have mercy

ócama- vb. "have mercy" (VT44:12-14; Tolkien may have abandoned this form in favour of órava-)

ócama-

verb. *to have mercy