Complex sentence: It is not believed that any Gaelic groups called themselves "Scoti" in ancient times, except when referring to themselves in Latin although in the 19th century "Aonghas MacCoinnich" of Glasgow proposed that it was derived from the Gaelic word "Sgaothaich".
Split into simpler sentences: It is not believed that any Gaelic groups called themselves "Scoti" in ancient times, except when referring to themselves in Latin. A History of England before the Norman Conquest In the 19th century "Aonghas MacCoinnich" of Glasgow proposed that "Scoti" was derived from the Gaelic word "Sgaothaich".