Dog Watch

Origin of naval phrase "dog watch" please

Dogwatch
A dogwatch at sea is the period between 4 and 6 p.m, the first dogwatch, or the period between 6 and 8 p.m., the second dog watch. The watches aboard ships are:

Noon to 4:00 p.m. Afternoon watch
4:00 p.m. to 6:00 p.m. First dogwatch
6:00 p.m. to 8:00 p.m. Second dogwatch
8:00 p.m. to midnight 1st night watch
Midnight to 4:00 a.m. Middle watch or mid watch
4:00 to 8:00 a.m. Morning watch
8:00 a.m. to noon Forenoon watch

The dogwatches are only two hours each so the same Sailors aren't always on duty at the same time each afternoon. Some experts say dogwatch is a corruption of dodge watch and others associate dogwatch with the fitful sleep of Sailors called dog sleep, because it is a stressful watch. But no one really knows the origin of this term, which was in use at least back to 1700.

Might it have anything to do with Sirius, the Dog Star? It would become visible about that hour.... (just guessing...)