The Collaborative International Dictionary of English v.0.48:
Invoke \In*voke"\, v. t. [imp. & p. p. Invoked; p. pr. & vb.
n. Invoking.] [F. invoquer, L. invocare; pref. in- in, on +
vocare to call, fr. vox voice. See Voice, and cf.
To call on for aid or protection; to invite earnestly or
solemnly; to summon; to address in prayer; to solicit or
demand by invocation; to implore; as, to invoke the Supreme
Being, or to invoke His and blessing.
Go, my dread lord, to your great grandsire's tomb, . .
Invoke his warlike spirit. --Shak.