Find filename of picture inserted in a Word Document on a Mac In a word document I included a pdf, that is a picture. 

However I forgot where is the source location and how it is called. 

Is there any way to find that out? 

I use Mac OS Mojave 10.14.5 on a Mac Book Pro and Microsoft Word for Mac Version 16.26.
There is a slight possibility that if you export your current document to a PDF, open it on Acrobat Reader, put your mouse over that image for a few seconds, a tooltip will come up and prompting you the original location of the image. 

However, since your image was imported through a PDF but not a direct file, this method may not 100% work.