Corsoldus was a Frisian king, a bit player in the frenetic post-Roman chaos in and around Gallia (Gaul) during the days immediately before it became France.
The name may be interesting if it is interpreted as ‘horse-lord’ (*Horswald), for this I think unusual name would then link to the Horsa of Hengist and Horsa fame. ‘Horsa’ could be considered a short form of something like ‘Horswald’, in turn giving the names Hengist and Horswald a dynastic appearance.