To coin a phrase - to use a cliche, or to take an obsure quote and give it a common usage. I get this feeling that it has something to do with coins being common, but I don't know where to look for that info.
If I'm not mistaken, this refers to the way pirates would seal a compact by signing said document with their own blood. Should they break their agreement, it would mean their death.
This refers to the act of going for it when interested in something, of seeing how deep your interest runs, and what will happen if you follow your dreams.
Most think this refers to that mushy, gushy, slushy way of signing a love letter. It actually refers to the act of sealing a marriage vow by kissing the bride. You may now kiss the bride.
A little more info: A tailor making a high quality suit uses more fabric than that which used with cheaper suits. The best suits are made from nine yards of fabric. This may seem like a lot but a custom suit does indeed take nine yards of fabric. This is because a really good suit has all the fabric cut in the same direction with the warp, or long strands of thread, parallel with the vertical line of the suit. This causes a great amount of waste in suit making, but if you want to go "dressed to the nines", you must pay for such waste.