Straining at gnuts(sic)? The later song, with the line you quote, is surely too recent for the reference to be intended - and there's no sign of it in the earlier one. Apart from that, the former is distinctly American in tone and unlikely to carry that link.

The simpler interpretation (always the best starting point!) is that he imagines HER eyes conveying that message to HIM.

Incidentally: fans of the author Patrick O'Brian's wonderful Aubrey/Maturin tales of the Napoleonic Wars at sea will recognise the "molly" reference.

Regards