Naff off - Get lost, go away (used as imperative)
Nag at - Repeatedly criticise someone verbally
Nail down - Succeed in getting, achieve - Understand fully - Get full information from someone - Succeed or achieve something
Name after - Give someone a name to remember another person
Nip off - Go somewhere quickly Nip out - Go somewhere quickly
Nod off - Fall asleep
Nose about - Look for something hidden or secret Nose around - Look around for evidence
Note down - Write something short like a phone number for future reference.
Nut out - Find an answer to a problem