Necessitate, v. t. [imp. & p. p. Necessitated; p. pr. & vb. n. Necessitating.]
Etymology: [Cf. L. necessitatus, p.p. of necessitare, and F. nécessiter. See Necessity.]
1. To make necessary or indispensable; to render unaviolable. Sickness [might] necessitate his removal from the court. South. This fact necessitates a second line. J. Peile.
2. To reduce to the necessity of; to force; to compel. The Marquis of Newcastle, being pressed on both sides, was necessitated to draw all his army into York. Clarendon.
Shades of meaning
Fernald has no entry of its own for necessitate; he lists it under compel.
He lists it without comment; the entries above explain its neighbors.