I can think of two ways to accomplish that, but neither of them are straightforward.
If you know how to do scripting, you could easily do that with ExifTool.
If not, it can be done with Photo Mechanic.
First you would use the Text export template in the Exporter dialog. You would have it output all selected images into a single file. Your export text would look like this:
{filenamebase}{tab}{keywords}{nl}
This will produce a file that you would use as a Code Replacement text file. Once created you would load the file into the Code Replacement dialog. Then you would create an IPTC Stationery Pad and put this in the Keywords field:
\{filenamebase}\
Apply that IPTC Stationery Pad to your TIFFs and the Keywords should transfer over. This method can be extended to transfer almost any field over to another image with the same base name.
HTH,
-Kirk