Luton is a corruption of "Lea-ton" meaning farm by the Lea. The earliest mention of the name is in the Anglo-Saxon Chronicle of the early 10th century. The name has undergone a variety of changes over the years, the modern form, though, occurring as early as 1195 in Feet of Fines rolls:

• Ligtun: 914;
• Lygtun: 917;
• Loitone: 1086-1158;
• Luitun: 1156-c. 1300;
• Luytun: 1156-c. 1300;
• Luiton: 1161-1415;
• Luitona: 1161-1415;
• Luyton: 1161-1415;
• Lutton: 1240-1381;
• Louytone: 1276;
• Lowton: 1291;
• Leuton: 1293;
• Lughton: 1376;
• Loughton: 1376.

Other names in the ancient parish included the following:

• Biscot (first recorded in 1086 as Bissopescote): "bishop's cottages";
• Bramingham (first mentioned as Bramblehangre in 1240): the earliest name meaning wood on a slope, with brambles growing on it;
• Cowridge (first mentioned as Curegge in 1196): "cow ridge";
• Crawley Green (first recorded in 1196 as Craulea): "crow clearing";
• Dallow (first mentioned in 1247 as Dolhou): the name mean dole-hoe, or a spur of land held in doles by a number of individuals;
• Farley (first mentioned as Ferleya in 1285): the Old English "fearnleah" meant fern, or bracken, covered clearing;
• Leagrave (first mentioned in 1224 as Littegraue): the meaning has nothing to do with the river Lea. One suggestion (in The Place Names of Bedfordshire & Huntingdonshire by A. Mawer and F. M. Stenton, published in 1926) is that the first element is a man's name - Lihtla, and so means Lihtla's grove. Other suggestions are light grove and little grove;
• Lewsey (first mentioned in 1291 as Leveseye): "Leof's island";
• Limbury (first recorded in 571 as Lygeanburg): "the fort on the River Lea";
• Luton Hoo: (first mentioned in 1276 as le Hoo): hoo, or hoe, means a hill, or spur of high ground;
• Mixeshill (first recorded in 1276 as Mixeweye): "dung road";
• Ramridge (first recorded in 1227 as Ramrugg): it may simply be ram ridge or it may mean raven ridge.
• Stopsley (first recorded as Stoppelee in 1199): "Stoppa's clearing";
• Warden Hill (first recorded in 1504 as Wardonhill): "watch hill";
• Whipperley (first recorded in 1285 as Wypereleya): the name may mean cornel tree clearing, according to Professor Zachrisson as related in The Place Names of Bedfordshire & Huntingdonshire by A. Mawer and F. M. Stenton, published in 1926. Cornels are deciduous trees originating in the Mediterranean and Far East.