I've only ever heard the first meaning, so I decided to look up the second one and what I found was interesting. Coffin nail is slang for cigarette, BUT in my entire life I've never heard anyone say that and I've spoken to people from several different countries and listened to lots of different English dialects. Since it is slang I would be careful using it. Just like how "fag" is a mean or derogatory word for someone who is gay it also means cigarette in the UK. So, what I'm saying is yes it does have two meanings but be careful using the second one. I hope this helps!