The author just quotes an old phrase without knowing the origin or meaning of the verb. It is/was the opposite of wane. The OED and Shorter Oxford definitions

The author just quotes an old phrase without knowing the origin or meaning of the verb. It is/was the opposite of wane. The OED and Shorter Oxford definitions explain the relevant sense of the verb: To start talking moderately, then gradually increase in potency or intensity. Quoting the OED's typically long entry: "Originally a more frequent synonym of GROW v. , which has now superseded it in general colloquial use, exc. with reference to the moon [...] confined to literary use, and have, in varying degrees, a somewhat archaic flavour; [...] The verb is said still to be current in certain dialects" While I have both of those dictionaries, the Shorter Oxford is the one I use and recommend.