Thats only with names that don't have history. Your dates are to new for the research I can put the Gillilands and the names that follow in 400 ad in Ireland. Their in history books and parish records and so on. Now with the locals and land yes the name does change but is still the same clan. Many records show clansmen adding letters to their name when they bought items form a market or ordered labor or made a contract. This was their way of accounting for such items or work done. But keep in mind that Gillilands were Irish not Scottish even though their family had been in upper Scotland for some decades they still had the traditional Irish ways at that time. They traveled back and forth to Ireland from Scotland by boat. They started from upper Ireland at DAL KIATA and traveled to Argyll in Scotland. This was at 500 ad when traffic was common in those areas because the distance is not far was easy to travel. At those time names meant everything. Since the original spelling changes to those of the land In Ireland (Gill) to those in Scotland when they followed St. Fillan.Now names at those time were spelled in three ways. Old Celtic, Norse Gaels (Gaelic), Ulaid Gaelic northern Ireland. Ulaid is so old most people never heard of it. But its still Gaelic in an old form. It was more in the terms of slang of 500 AD Goidelic. But then you find the langauge changes farther you go south in Ireland. Not much just more slang. Until you find most of the original language is 3000 BC Phoenician (Punic). This languages changes over hundreds of years do to writings. Almost like they invented a language from scratch. Since this language changed because of less of population speaking it finally went extinct. Many ancient writings in Phoenician (Punic) were in the famous Alexandria library which was burned down in 642 A.D. Most people learned many new languages to mix in. So the name is important because of the way and place were they lived. Neat thing about culture at that time was they marked everything in writing or symbols.