needs(r = adv.all) inevitably, necessarily, of necessity - in such a manner as could not be otherwise; "it is necessarily so"; "we must needs by objective"

   Of necessity; necessarily; indispensably; -- often with must, and equivalent to of need. [1913 Webster]
"A man must needs love mauger his head." [1913 Webster]
"And he must needs go through Samaria." [1913 Webster]
"He would needs know the cause of his repulse." [1913 Webster]

needs, adv. archaic (usu. prec. or foll. by must) of necessity (must needs decide).

Etymology:
OE nedes (as NEED, -S(3))