Could you just call it suponified fat?
nope, there again you would be hiding the truth because saponified fat could be anything....beef fat, pig fat, vegetable fat. The only way to list lard is LARD.
There are people who want to avoid certain ingredients in soap for various reasons, as stated above...religious or ethical.
Put yourself in the customers shoes. Would you want the person you were buying from to be COMPLETELY HONEST about the ingredients they were using??? Of course you would. Especially if it was against your religion to use any products with lard in it or if you were vegetarian or vegan.
Instead of hiding the truth try and educate your customers on the ingredients you chose. Why did you choose lard? For me it's because lard makes excellent soap with a creamy lather you just can't duplicate with veggie oils, Lard is similar in fatty acid composition to Olive, I can purchase lard locally which cuts down on costs because I don't have to pay for shipping. Just my 2 cents.