The term Navvy has been around since the beginning of the 19th century, and has always been used to refer common laborers on any project which requires digging/excavation: canals, earthworks, pipelines, levees, railroads. Later, when a machine was developed to do this work, it was called--as one might expect--the steam navvy. The term was, indeed, taken from the word navigator, but not in any way limited to seafaring--more having to do with surveying.

The tow-path driver responsible for the draft animals which towed barges and canal boats on the old canal systems was known as the HOGGY; that possibly might be the basis for the term hog-eye, through folk etymology.