Why is slug in publishing called a slug? [closed]

Slug as we know on the internet from the articles (example https://www.rollingstone.com/music/music-lists/best-albums-of-all-time-1062063/ 'music-lists/best-albums-of-all-time-1062063' being the slug in question) doesn't seem to be in any way related to an animal slug or a sluggish person. I wonder how it got the name to stick? Maybe it is an acronym for something ('Shortened Label Unique Globally' (just joking, I made this one up))?

Yes, one definition of slug is an identifying line. It may be related to a slug as a line of type set as a unit by a printer:

Merriam-Webster, definition 6 of slug:

https://www.merriam-webster.com/dictionary/slug

b : a line of type cast as one piece

c : a usually temporary type line serving to instruct or identify