A midshipman originally was, as the name suggests, one who lived amidships, this is mid-way between the officers who lived aft and the men who lived forward. While training as an officer he worked with the men somewhat like our own cadets. In the U.S. Navy this original status is more closely maintained, the U.S.N. midshipman ranking with the R.C.N. cadet. The midshipman used to serve seven years on the lower deck and was roughly equivalent to our present day petty officer in rank and position.
The midshipman's white patch, as an insignia of rank, came into use in 1758. It has been suggested that the patch is all that remains of what used to be a white coat collar which went out of use because the 'Young Gentlemen' used to dirty it too quickly. No support can be found for this doubtful theory. The significance of white, however, is of great antiquity; to it our word candidate is related. Candidus, Latin adjective for white, referred to the pure colour of the togas worn by those aspiring to high office in the Roman government. The same purity motif is seen with a bride's wedding dress. The midshipman's white patch and the officer candidate's white cap ribbon probably stem from this Roman origin.