A Lieutenant often takes the place of a superior officer when that officer is absent. The word comes from the French lieu (place) and tenant (holder). The Lieutenant then is one who holds the place of another. Since he took the place of a senior officer the Lieutenant ranked next to that person and was his deputy. Such was the case for Lieutenant General and Lieutenant Colonel, which I will discuss later. The Navy Lieutenant Commander came about in a different way, which I will also discuss later. Those who served with Captains might have been called Lieutenant Captains but that title did not survive as a rank.
There may have been Lieutenants aboard British warships as early as the Twelfth Century when the ships carried groups of soldiers to do whatever fighting was necessary. A Captain commanded the soldiers and he might have had a Lieutenant. The rank appeared officially in the British navy about 1580 but soon disappeared. It became a designated rank in 1650 as the rank given to noblemen in training to become Captains. At that time there were no other ranks below Captain so there could be three grades of Lieutenants on a ship--first, second and third.
The Lieutenant has been a part of our Navy since its beginning in 1775. In 1862 the Lieutenant's rank insignia was two gold bars. These became silver in 1877. In 1874 Lieutenants began wearing the sleeve stripes of two one-half-inch wide strips of gold lace.
The rank below Lieutenant in the early days of our Navy was Sailing Master, later Master, a Warrant Officer. After 1855 graduates of the Naval Academy filled those positions. Their complete title was "Master in line for Promotion" to distinguish them from the Warrant Masters who would not be promoted. In 1883 the rank became Lieutenant, Junior Grade. In 1862 the Masters wore a gold bar for rank insignia, which became a silver bar in 1877. In 1881 they started wearing their current sleeve stripes of one one-half-inch and one one-quarter-inch wide strips of gold lace.
On land, there had been Lieutenants in the British and other armies for several centuries so it was logical to have the rank on duty in 1775 with our Army. About 1832 First Lieutenants, except those in the Infantry, began wearing a bar--a gold one--on their shoulder straps as rank insignia. The bar had to be the same color as the borders of their shoulder straps, which were gold. Infantry First Lieutenants, however, wore shoulder straps with silver borders so their bars were of silver. After 1851 all Army officers wore shoulder straps with gold borders so the Infantry First Lieutenants then wore gold bars. The situation was just the opposite when First Lieutenants wore their dress uniforms, which had gold epaulettes. Their rank insignia had to contrast with the gold so they wore silver bars. In 1872 the Army cleared up the confusion and made the bars on shoulder straps silver as well. Second Lieutenants did not have rank insignia but wore epaulettes or shoulder straps so their uniforms identified them as officers. When officers and enlisted men both started wearing khaki uniforms with plain shoulder straps during the Spanish-American War it became more difficult to recognize the Second Lieutenant. Other officers wore metal rank insignia on their shoulder straps or collars. In 1917 the Army settled that problem by making the gold bar the Second Lieutenant's badge of rank.
From: Why is the Colonel Called "Kernal"? The Origin of the Ranks and Rank Insignia Now Used by the United States Armed Forces
Information borrowed Naval Historical Center
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