'Maidenhead' comes from Maiden Hythe, a wharf on the Thames.
Hythe means wharf, as in Rotherhithe; the 'maiden' part is harder to explain. It may mean new – the new wharf – or refer to maidens, perhaps a place where women gathered; timber (moed) and rubbish (midden) have also been suggested. The town took the name Maidenhythe, first recorded in 1296, after a new wharf was built by the bridge of about 1280, replacing the older name South Ellington.