From The Collaborative International Dictionary of English v.0.48:
Nudge \Nudge\ (n[u^]j), v. t. [imp. & p. p. Nudged (n[u^]jd);
p. pr. & vb. n. Nudging.] [Cf. Prov. G. kn["u]tschen to
squeeze, pinch, E. Knock.]
To touch gently, as with the elbow, in order to call
attention or convey intimation.