| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 841 | Sugyn | Welsh | Legendary son of Sugynedydd. | M | |
| 842 | Sulyen | Welsh | Legendary son of Iaen. | M | |
| 843 | Syvwkh | Welsh | Legendary son of Cleddyv KyvwIch. | M | |
| 844 | Tad | Welsh | Father. | M | |
| 845 | Tadd | Welsh | Father. | M | |
| 846 | Taffy | Welsh | Diminutive of David: Beloved or friend, from the Hebrew. Sixth century St David (or Dewi) was patron saint of Wales. | M | |
| 847 | Talaith | Welsh | Diadem. | F | |
| 848 | Talar | Welsh | From the headland in the field. | F | |
| 849 | Taliesin | Welsh | Handsome; radiant brow. 6th century Welsh bard and author of the Book of Taliesin. | M | |
| 850 | Talyessin | Welsh | Handsome. | M | |
| 851 | Tangwen | Welsh | Legendary daughter of Gweir. | F | |
| 852 | Taren | Welsh | Thunder. | M | |
| 853 | Tarian | Welsh | Shield. | F | |
| 854 | Tarran | Welsh | Thunder. | M | |
| 855 | Tarrant | Welsh | Thunder. | M | |
| 856 | Tarren | Welsh | From the knoll. | F | |
| 857 | Taryn | Welsh | Thunder. | M | |
| 858 | Tegan | Welsh | Beautiful. | F | |
| 859 | Tegwan | Welsh | Beautiful and fair. | F | |
| 860 | Teithi | Welsh | Legendary son of Gwynnan. | M | |