The Collaborative International Dictionary of English v.0.48:
Anonymously \A*non"y*mous*ly\ ([.a]*n[o^]n"[i^]*m[u^]s*l[y^]), adv. In an anonymous manner; without a name. --Swift. [1913 Webster]WordNet (r) 3.0 (2006):
anonymously adv 1: without giving a name; "she wrote these letters anonymously"