Stephen Maturin of Patrick O'Brian's Aubrey-Maturin series makes the pun that the dog watch is so-named because it is 'cur-tailed' ('curtailed', i.e. Another variation is that those sleeping get only ' dog sleep' in this watch.

An alternative folk etymology is that the name arose because someone tasked with one of these 'half' watches was said to be 'dodging the watch', taking or standing the 'dodge watch'. The name is also said to be derived from Sirius, the 'Dog Star', on the claim that Sirius was the first star that can be seen at night. It originally referred to the night-watch on ships - that is, the time when (on land) all but the dog were asleep.

The Oxford English Dictionary states that the word 'dogwatch' is a direct translation from either German or Dutch of a similar term. The choice of time also allows both watches, if there are only two, to eat an evening meal at about the traditional time. This allowed the sailors to stand different watches instead of one team being forced to stand the mid-watch every night. The reason behind this watch's existence is that, in order for the crew to rotate through all the watches, it was necessary to split one of the watches in half, to create an odd number of watches in a ship's day. Each of these watches is half the length of a standard watch. This period is split into two, with the 'first' dog watch from 16:00 to 18:00 (4 pm to 6 pm) and the 'last' dog watch from 18:00 to 20:00 (6 pm to 8 pm) (there is no 'second' dog watch). Dog watch, in marine or naval terminology, is a watch, a period of work duty or a work shift, between 16:00 and 20:00 (4 pm and 8 pm).

Dogwatch meaning