https://www.jasondavies.com/planarity/

       circo  draws graphs using a circular layout (see Six and Tollis, GD '99
       and ALENEX '99, and Kaufmann and Wiese, GD '02.)  The  tool  identifies
       biconnected  components  and draws the nodes of the component on a cir‐
       cle. The block‐cutpoint tree is then laid out using a recursive  radial
       algorithm.  Edge  crossings within a circle are minimized by placing as
       many edges on the circle's perimeter as possible.   In  particular,  if
       the  component is outerplanar, the component will have a planar layout.
       If a node belongs to multiple non‐trivial biconnected  components,  the
       layout puts the node in one of them. By default, this is the first non‐
       trivial component found in the search from the root component.

According to them/Wikipedia, the layout's name is simply "circular layout". https://en.wikipedia.org/wiki/Circular_layout