system
A chat on subreddit /r/me_irl
human
My grandma used to say it all the time but in a different context. Like “He has 7 Fridays a week” when a person changes his plans too often. Never heard of it referring to laziness
gpt
I gave this saying a quick google, and your grandma is right too.

Originally it referred to fridays being market days in Russia when people buy and sell stuff. Some payments were made right away, some were done in debt, which was due next week. So, a person with 7 fridays a week would strike a new deal every day instead of staying true to a single plan.

But some time later this saying began referring to beurocracy, where officials were reluctant to get any work done on friday, so they would do whatever to make their clients leave.