I've lost ye plotte, guys!
Sherwood, Duane, is still a substantial swathe of forest and never was all woodland. It is a tourist magnet and the well used parts are being degraded by pressure of visitors. The term Forest in medieval times and since can refer to a whole area of mixed woodland, heath and other terrain. The legends, stories and films of Robin Hood have led us to believe that the outlaws lived exclusively amongst the trees. They may have done but there's no evidence.
The Oxford Dic gives:
Forest
Origin: Middle English (in the sense 'wooded area kept for hunting', also denoting any uncultivated land): via Old French from late Latin forestis (silva), literally '(wood) outside', from Latin foris 'outside' (see foreign).
John