(St.), formerly called St. Wylgeforte. “Women changed her name” (says Sir Thomas More) “because they reken that for a pecke of otys she will not faile to uncumber them of their husbondys.” The tradition says that the saint was very beautiful, but, wishing to lead a single life, prayed that she might have a beard, after which she was no more cumbered with lovers. “For a peck of oats,” says Sir Thomas More, “she would provide a horse for an evil housebonde to ride to the Devill upon.”
“If a wife were weary of a husband, she offered oats at Poules ... to St. Uncumber.” —Michael Woode (1554).
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894