........ may the Lord make us truly thankful.

I’ve repeated this hundreds of times before tucking in to the school meal at grammar school (no problems in the UK mixing religion and state education, at least not back in the 50s/60s). It’s just hit me that I haven’t a clue as to its source. A (confessedly) cursory google brought no joy. Any ideas?

BTW in the penultimate sentence above I wanted to write,

1 An (admittedly) cursory google

No, I thought, that won’t do.

2 A (admittedly) cursory google.?

Shudder. That’s much worse. My solution was as above, although

3 A google, albeit cursory, etc

might have been more felicitous. But, whilst 1 and 2 are stylistic nonos, are either or both correct in a strictly grammatical sense? Or neither?

I’m certainly not an expert here, so I’m just as curious as you, aldi, but when I’m faced with these sorts of questions, I go with what would sound right if the sentence was spoken and not by what the construction of the written sentence seems to suggest.

Or you could go all radical fundamentalist prescriptivist and say that any instance of the assimilation of the N of AN into the following word is wrong, wrong, wrong and one should never use the bare A.

I found this in Reminiscences of Methodism in West Jersey, by G.A. Raybold, 1849:

Crowds attended, the house was filled, all were anxiously waiting; but there was no preacher. At last the man arose, saying, “Well, something must be done; the old woman must be buried. We will try to pray, anyhow.” He began to say, “Our Father, who art in heaven—Now I lay me down to sleep;” ending with, “For what we are about to receive of they creature comforts, O Lord, make us thankful.” One lively person present exclaimed, “Oh dear! is he a-going to make us eat the old woman?”

(Source: Google Books)

Clearly, it was a cliché back then.

I do not know the precise answer to your question about the origin of the prayer, Aldi, but it can be found in the Anglican Book of Common Prayer, and you might focus your research in that direction.  I’m guessing it goes pretty far back.

I did some checking in that direction, and it seems to have been a fairly recent (latter 20th century) addition to the Book of Common Prayer.  I’m pretty sure that it was added to the BCP after having become widely used, rather than originating in the BCP.

Charles Dickens used the prayer in Nicholas Nickleby (1838):

whereupon Mr. Squeers said, in a solemn voice, ‘For what we have received, may the Lord make us truly thankful!’

Since Mr. Squeers had no original thoughts, it must have been a widely used and recognized prayer even then.