From the negative prefix *ne and ke/rdos "gain/profit."
Likewise or similarly glossed in other lexica (references at Photius nu183 Theodoridis), and cf. also a scholion on Homer, Iliad 17.469, where the headword occurs in the accusative singular, modifying boulh/n "counsel" (web address 1).
Properly, the prefix takes the form nh- when *ne- is elided before an initial vowel, as in nhlh/s (nu 313), nhmerth/s (nu 317), nh/nemos (nu 319); but nh- is analogically extended to roots beginning with consonants, as here and in nhpenqh/s (nu 321).