[quietbritishjim]

Punt is a long gamble, most often used as part of "take a punt". As you say, probably related to football usage.

I don't know if punter (as in, customer) is related. I suppose buying something is always a bit of a punt to some extent.

[rcxdude]

They are related, it seems. punter being gambler but evolving into general 'customer/member of the public' over time.