Greetings:

Yes, it's called earthshine, but it needs some explanation. Sometimes enough sunlight is reflected from the Earth's surface to faintly illuminate the otherwise invisible New Moon. Put another way, light from the Sun strikes the Earth, is reflected to the Moon, and in turn is reflected back to our receptive eyes back here on Earth.

In the case of Sir Patrick Spens (or Spencer), there was still a thin crescent of the Old Moon shining, probably because it was the night before the true New Moon. That crescent made up the "arms" which held the New Moon, visible because of earthshine. Such a phenomenon was once considered a sign of bad luck.

--- Steve