orillar
edge
orilla
edge, shore
+
-ar
verb suffix
Orillar means to edge and can be thought of as orilla0 (edge or shore0) + -ar1 (verb1), literally meaning 'to put an edge on' or 'to go along the edge'.
verb
  1. edge
    To move to or stay at the edge or border of something.
    El barco comenzó a orillar la costa para evitar las rocas. // The boat began to skirt the coast to avoid the rocks.