As a St David’s Day present, here are the entries from Llewellyn’s Complete Book of Names for David and Dewi.
David ♂ Biblical name of Hebrew origin. The meaning isn’t all that clear, but seems mostly likely to derive from a root meaning “beloved,” although, interestingly enough, the Hebrew letters which make up the name David are exactly the same ones used for “mandrake.” 12th C. St. David is the famous leek- and daffodil-wielding patron saint of Wales — but his real name was actually DEWI.
Diminutive forms: Dawe (historic); Dave, Davey, Davie, Davy.
David in other languages: Welsh: Dafydd; Dai (diminutive), Irish: Dáibhead, Daithí, Gaelic: Dàibheid, Dàibhidh, Cornish: Daveth, Czech, French, German, Portuguese, Romanian, Russian, Serbian, Spanish: David, Hungarian: Dávid, Lithuanian: Davidas, Italian: Davide, Latvian: Dāvids, Pol: Dawid, Arabic: Da’wud, Hawaiian: Kāwika, Maori: Rāwiri, Finish: Taavetti, Taavi (diminutive).
Bearers: two medieval Scottish kings (d. 1153 and 1371); David Copperfield, the eponymous hero of Dickens’s 1850 novel, and the stage-name of American illusionist David Kotkin (b. 1956); David Lloyd George, 1st Earl Lloyd-George, (1863–1945) and David Cameron (b. 1966), both British Prime Ministers; David Eddings (1931–2009), the American novelist; David Bowie (b. 1947), the British singer-songwriter.
Dewi ♂ ♀ The boy’s name Dewi is a very old and very interesting name. Dewi Sant is the Welsh name for St. David, and many people believe it is simply the Welsh form of David. It isn’t. David is simply the name adopted to render Dewi in English, a long time ago. Almost certainly, his name actually derives from the Common Celtic *dOEwo- “(a) God,” cognate with Zeus, Latin deus, Sanskrit deva and the Irish Dagda, etc.
The element is well attested in given names in the Roman period — examples include Deomiorix, Deiana, and Deieda. Some have attempted to derive the name from Dewydd, an alleged “old form” of Dafydd—the Welsh form of David — but the argument works just as well the other way — Dewydd may well represent an attempt to synthesize Dewi and Dafydd. The simple fact is, biblical names were not used in sub-Roman Britain, and thus the likelihood of someone genuinely being called “David” in sixth-century Wales is, quite frankly, about as likely as someone in the period being called Jayden.
Dewi was used as a given name in the Middle Ages, probably in honor of the saint, but then disappeared until its revival in Wales in the nineteenth century.
By coincidence, the Malaysian girl’s name Dewi means “Goddess.”
I love coincidences!
Dydd Gŵyl Dewi hapus!