Of uncertain origin. It is found in Old French as Yolande, of which this is a Latinate form. It may be ultimately of Germanic origin, but if so it has been altered beyond recognition. It is also sometimes identified with the name of St Jolenta (d. 1298), daughter of the king of Hungary.
French: topographic name for someone who lived by a quickset fence, Old French pleis (from Latin plexum past participle of plectere ‘plait’, ‘weave’), with fused preposition and definite article du ‘from the’. This is a Huguenot name, well established in South Africa and elsewhere.