Why do you think Googlebot would make these requests when they do not exist? (There are no such links on my sites - yup, more than one.)

 66.249.75.154 "GET /QXYoZ/ HTTP/1.1" 404 160 "-" "... Googlebot/2.1..."
 66.249.79.148 "GET /ZlPmZ/ HTTP/1.1" 404 160 "-" "... Googlebot/2.1..."
 66.249.69.116 "GET /OVQfZ/ HTTP/1.1" 404 160 "-" "... Googlebot/2.1..."
 66.249.79.88 "GET /RPKLZ/ HTTP/1.1" 404 160 "-" "... Googlebot/2.1..."

Then I discovered other Bots doing the same:

 "GET /XNmLZ/ HTTP/1.0" 404 160 "-" "CCBot/2.0 (http://commoncrawl.org/faq/)"
 "GET /UcLaZ/ HTTP/1.1" 404 160 "-" "Mozilla/5.0 (compatible; YandexBot/3.0; ..."
 "GET /KfcTZ/ HTTP/1.1" 404 160 "-" "Mozilla/5.0 (compatible; Baiduspider/2.0; ..."

Then random IPs (typical exploit bots) try for similar URIs. Here is a really odd one:

 "GET /LfYgZ/MPUfZ/XfhOZ/XeXLZ/XhhdZ/RZXbZ/QdpXZ/MhUMZ/ HTTP/1.1"

Somewhere, me thinks, is someone - who knows who or why - has links to my sites like these. (I've seen SemrushBot publish pages to an old site of mine with invalid links.)

For there are been some referers like:

 "GET / HTTP/1.1" 200 11592 "http://www.example.com/SRjUZ/"
 "GET / HTTP/1.1" 200 408 "http://www.example.com/SLhcZ/"

And these obvious exploiters:

 "GET /wp-login.php HTTP/1.1" 404 3 "http://www.example.com/PTfRZ/wp-login.php"
 "GET /wp-login.php HTTP/1.1" 404 3 "http://www.example.com/UeWfZ/wp-login.php"
 "GET /KOlQZ/wp-login.php HTTP/1.1" 404 3 "http://www.example.com/wp-login.php"

Exploits grow exponentially...

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