I all it advertising clause, because I remember still in the 2000s seeing an Apple ad which at the end of it showed "Unix" or something like that on it, and I remembered that was one of the BSD license requirements, or maybe Apple just did it also just to proudly boast using Unix.
Hmm… I may be confusing the following clause from the “new” BSD license with the advertising clause from the original BSD license.
> 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
The 2-clause BSD license omits even that.