Tawdry is a saint's name that got worn down to a single word.
Audrey was a seventh-century queen of Northumbria who died in 679. Her Old English name was Æðelðryð, also rendered Etheldreda. Etymonline says that according to Bede, she believed a throat tumor was God's punishment for her youthful fondness for necklaces. Southey speculated that she may instead have worn lace to hide a scrofulous neck. Merriam-Webster adds that she gave up her royal position to become a nun and that her shrine became a major pilgrimage site.
An annual fair in her honor was held at Ely on October 17. Vendors sold cheap trinkets there, including a lace necklace or ribbon known as "St. Audrey's lace." Over time, Etymonline says, the phrase became "tawdry lace," and the -t- was added through misdivision with "Saint," so the "t" of "Saint" attached itself to "Audrey." Etymonline dates "tawdry lace" to the 1540s.
The goods were by then associated with rustic finery. Etymonline notes that the necklaces came to stand for a cheap, rustic look, especially as worn by country girls. The phrase was then clipped to tawdry by itself. The adjective followed, describing something no longer fresh or elegant but displayed as though it were, or a cheap, showy imitation of something costly.
Dictionaries disagree on the dates. Etymonline gives the noun in the 1610s and the adjective in the 1670s, while Merriam-Webster records the adjective in 1655 and the noun around 1680. Both agree on the chain from St. Audrey's lace to tawdry lace to tawdry.
There is an irony in it. A woman who reportedly regretted her own jewelry gave her name to a market in cheap jewelry. Etymonline also lists tawdrum, an old word for a tawdry decoration.
And Audrey herself survived as a personal name, first recorded in the 13th century, descended from the same Æðelðryð.