This could be anything. It doesn't look much like an attack (although it could be an attempt to pollute your search results - but it's a 404 anyway so no worries there, although it's polluting your reports).
Note that if GSC is reporting these 404s then it must have found and crawled these URLs from somewhere, either through a misconfiguration on your site or by someone linking to you in this manner.
Click on the URL in Google's 404 report and drill down to find out where these links are coming from - that should give you a big clue as to what's happening.
usg look like URL parameters used in Google search. But why they would appear on the actual URL requested from your site is a mystery. A misconfiguration somewhere perhaps? Maybe there is a bot crawling Google SERPs and constructing (malformed) links from what it finds?!