This is a good reference for soap labeling for US soapmakers:
Quick Labeling FAQ - Marie Gale
Particularly:
What goes on the BACK or SIDE panels?
For
all products:
- The name and address of the responsible party.
- Directions for safe use (if applicable)
More detail is available on various pages on the website.
Since you don't say if you are doing this for profit (selling) or as a gift to a friend, I ask, which is it? Are you being paid for these soaps up-front? Or are you doing a favor for a friend or family?
If you are selling it, it is a Consumer Commodity and therefore etiquette has nothing to do with, but you have to follow US Federal law in the Fair Packaging and Labeling Act (
see this link)
If you are already in business and are getting paid for your product, then you really should know the rules and regulations of all the pertinent agencies regarding labeling laws. It takes a lot of dedication to delve though it all, but it can save you headaches in the future by avoiding legal hassles.
Here is another link to read regarding, how a soapmaker making claims about their soap can put them into the cosmetic category, leading to even more legal ramifications. It is well worth reading because it happens all the time (claims about soap turning it into either a cosmetic or a drug or both).
ETA: If you are not selling, but plan to or even think you may in the future, then it's a good time to start practicing proper labeling because you'll have to learn it anyway. And even if you're not ever going to sell, why not learn it since it's really the right thing to do, to label your product shared with others.