It’s either the water pump leaking or the timing cover itself. Coolant flows through a couple of passageways in the timing chain cover and with time, aged coolant, etc. the gasket between the cover and the engine block can rot out.
Even the cover itself can rot. It’s aluminum and chronic leakage in that area will erode the aluminum. It may be time for a new cover and if you’re that far in then a new timing chain should be considered. Hope that helps.
(And timing cover leaks are not rare either)