Kegitua em Powys 12g., Kegidua 1254, Kegidua, Kegitua 1265, (pencenedl de) Kykydua 1271, Kekydena 1310, Kekydeva 1376, Kegitiva 1379, 1401, ynghegitua 15g., Kegidva ar ôl 1505, Kegidfa c.1566
Guildesfield, -ffelde 1278, Guldesfeld’ 1286, Guldeffeld 1288, 1329-30, Guldesfeld 1329, 1402, Gillesfeld 1535, Gylsefelde 1547, Guilsfielde 1588, Gilsfild 1597, Guildsfielde 1747-8

The Welsh name ‘Cegidfa’ means ‘place of hemlock’ with cegid 'hemlock' and ma, lenition -fa. The English name probably means 'open land where golden flowers are found' and may be a loose translation of the older Welsh name. The first element is likely to be Old English gylde 'golden flowering plant' especially the plant family umbelliferae such as the wild parsnip, rock samphire and fennel. Members of the same family include cegiden 'dropwort', cegiden wen 'great chervil' and cegiden y dwr 'cowbane'. English field once meant 'open land', later acquiring the sense 'enclosure, enclosed field'.