Wax lyrical - origins of phrase?

Question

What are origins of this phrase?

Answer 1

Found this explanation on phrases.org.uk

-

'The intransitive verb to wax is normally seen in the sense of increasing, as the moon waxes and wanes in its cycle. But to wax also means to become, to tend towards, to grow towards. One can wax indignant, or wax lyrical, or wax rapturous, meaning you become/tend to that state. The word is old, tracing back from the high German to the Greek'.