knag / nag [næg]
knag – n. – 1. obsolete a short projection or spur, especially from a tree trunk or branch; 2. archaic a wooden peg for hanging things on; 3. obsolete a prong of an antler
nag – n. & v. – n. – 1. a persistently nagging person; 2. an old broken-down horse; 3. slang a race horse; 4. a small riding horse or pony; v. – 1. annoy or irritate with persistent fault-finding, complaining; 2. (of a pain) ache dully but persistently; 3. worry or preoccupy