nag 1 
(năg)
(năg)v. nagged, nag·ging, nags
v.tr.
1. To annoy by constant scolding, complaining, or urging.
2. To torment persistently, as with anxiety or pain.
v.intr.
1. To scold, complain, or find fault constantly: nagging at the children.
2. To be a constant source of anxiety or annoyance: The half-remembered quotation nagged at my mind.
n.
One who nags.
[Probably of Scandinavian origin; akin to Old Norse gnaga, to bite, gnaw.]
nagger n.
nagging·ly adv.