The name Lachlan is a Scottish Gaelic name derived from the old Gaelic word "lachan," meaning "lake." It is believed to have originated in the region of Argyll in western Scotland, where many lochs or lakes are present. The name was likely initially used to describe someone who lived near a lake or was associated with a particular body of water.

During the Middle Ages, the name Lachlan appeared in various Scottish historical records and documents. One of the earliest recorded instances was Lachlan Mor, who was a 13th-century Scottish warrior and chieftain of the Clan MacLachlan. He played a significant role in defending Scotland against the Norse invaders and is celebrated in Scottish folklore.

In the 16th century, Lachlan Macintosh, born around 1520, was a notable figure who served as the 16th Chief of Clan Mackintosh. He was known for his involvement in the battles of the Scottish Reformation and his efforts to protect the interests of his clan.

Another noteworthy bearer of the name was Lachlan Macquarie, born in 1762, who was a British colonial administrator and served as the Governor of New South Wales from 1810 to 1821. He played a crucial role in the development of Sydney and is credited with shaping the infrastructure and governance of the colony during his tenure.

In the 19th century, Lachlan McLean, born in 1798, was a Scottish-Canadian explorer and fur trader who worked for the Hudson's Bay Company. He is remembered for his expeditions in what is now western Canada and his contributions to the exploration of the Pacific Northwest region.

More recently, Lachlan Murdoch, born in 1971, is a prominent Australian-American businessman and media executive. He is the co-chairman and CEO of the media conglomerate News Corp, founded by his father, Rupert Murdoch, and has played a significant role in the company's global operations.

While the name Lachlan has Scottish origins, it has gained popularity in various parts of the world, particularly in Australia, New Zealand, and North America, where it is often associated with Scottish heritage and traditions.