Fine words butter no parsnips

Does anyone know the origin of the saying 'Fine words butter no parsnips'? Although I do understand what it means now, as a child I was mystified by its meaning

The earliest known example of the phrase dates from 1639, in the form "Faire words butter no parsnips". Anybody who has ever eaten boiled parsnips knows that they cry out to be glazed in butter before serving, and in traditional English cookery they invariably are - it is a necessary part of their preparation. The point of the phrase is that words alone achieve nothing - a person may "butter you up" with fine words, but he can't butter parsnips with them! (VSD)

Truly spoken, and a reminder that parsnips are what people ate before they had potatoes. This saying has to go back a long way before the 17th century.
SS