How to tag files (with Finder tags) using parts of a file name?
orig=/path/to/tagged-file
folder=/path/to/folder
string=*abc*
find "${folder}" -name "${string}" \
                 -exec xattr -wx com.apple.metadata:_kMDItemUserTags \
                       "$(xattr -px com.apple.metadata:_kMDItemUserTags '${orig}')" \
                       {} \;



Create a file with the tags that you wish to apply to a certain set of files that will match a search string. In the script above, this file is located at /path/to/tagged-file and is set on the first line of the script to the orig variable. Replace this with the path to the file that you've created.
On the second line of the script, change the path to the path of the containing folder that you wish to search through. This will be set to a variable called folder.
On the third line, set the string to search for in the name of the file. *abc* will match 123abc123.txt.
The fourth line and beyond is actually a single line that runs the find command to find the matching files then xattr to copy the tags from that original file to every file found.