Lestvne 1086, Lecton’ 1245, Lehgtone 1284, Lechton 1309, Leghton 1390, 1540-1, Leighton 1399, 1583, Leyghton c.1540, Layton 1662, Thley 1303, Y Llai mid 15th cent, (plas yn) y llai mid 16th c, y llai ymhowys late16thcent, Llai neu Leighton c.1700
OE lēac and tūn, literally ‘farmstead, estate, etc where leeks grow’ or simply ‘leek enclosure, a herb garden’. The Welsh form Y Llai must derive from a late form such as Le(i)ghton in which the earlier -c-had already been lost and the place-name pronounced very closely to the modern 'Layton'; the original difference in place-name between Old English leac and leah, wood, clearing, had disappeared before Y Llai developed. There are similarities with Coed-llai, the Welsh name for Leeswood Flintshire, and Llay or Llai, Denbighshire which are thought to contain llai as a borrowing from Old English leah, 'wood, clearing'. Tre'r-llai is now used as the official Welsh name for Leighton but there is very little historical evidence to confirm it.