Unsaponifiable

Unsaponifiables are components of an oily (oil, fat, wax) mixture that fail to form soaps when blended with sodium hydroxide (lye) or potassium hydroxide. Since saponifiable components of the original oil mixture do form soaps, the result of a soap making procedure is a mixture of soaps and other, frequently oily, materials.

Unsaponifiable constituents are an important consideration when selecting oil mixtures for the manufacture of soaps. Unsaponifiables can be beneficial to a soap formula because they may have properties such as moisturization, conditioning, vitamins, , etc. On the other hand, if the proportion of unsaponifiables is too high, or the specific unsaponifiables present do not provide significant benefits, a defective or inferior soap product can result.

The percentage of unsaponifiable material varies per substance:

...
Wikipedia