The earliest record of the rhyme is in Tommy Thumb's Pretty Song Book, published c. 1744, which noted only the first four verses. The extended version was not printed until c. 1770. I learned this from Lomax's Folk Songs of North America. It is also found in Cecil Sharp's English Folk Songs of the Southern Appalachians. Several of the verses, particularly the descriptions of the burial with the "silver spade" and the "Golden chain", are similar to those in "Stormalong" and "Deep Blue Sea". This came to be a running joke at the annual Christmas parties of the Messiah Lutheran Church choir after it came up in a game and no one believed it was real. Several of us provided proof and when the subject of obscure songs came up again, someone was sure to mention Cock Robin. Here are two illustrations from printed versions of the nursery rhyme: