From Wiktionary, the free dictionary
Borrowed from Sanskrit नीरस (nīrasa); By surface analysis, നീ- (nī-) + രസം (rasaṁ).
നീരസം • (nīrasaṁ)
- distaste; displease
- resentment
- Gundert, Hermann (1872) “നീരസം”, in A Malayalam and English dictionary, Mangalore, London: C. Stolz; Trübner & Co.