NW means North West, then what ('ly) means?

It’s short for -erly as in ‘northwesterly’ meaning that it’s located in or moving toward.

In a generally, NW direction. Similar to Northerly, Southerly, Easterly, etc. also be aware of Nor’east, nor’easter, nor’westerly, sou’west, etc. This is the most basic sort of nautical terminology that anyone aspiring to be a seaman must know.

Thanks gents