I had never heard that expression before [1]. Is 'TOIL' cultural, or is it just that I am inexperienced having never been an employee?

[1] https://factorialhr.com/blog/time-in-lieu-explained/

I assume it's widespread in more developed nations/places with familiar employee rights, since it's pretty basic really - you worked when you shouldn't, here's time off to compensate.

Unless you just meant the acronym - that I'm aware of but wouldn't say it's as common as the concept. To me 'toil' is firstly an English word, secondly an SRE term, and only distantly third 'time off in lieu'.

It's definitely common in the UK.

Time off in lieu or the acronym? I've had time off in lieu but I have never seen that acronym before.

It's also a thing in canada