Anonymously

without any name acknowledged, as that of author, contributor, or the like:
an anonymous letter to the editor; an anonymous donation.
of unknown name; whose name is withheld:
an anonymous author.
lacking individuality, unique character, or distinction:
an endless row of drab, anonymous houses.
contemporary examples

the article, by jonathan strong, is rife with scaremongering, anonymously sourced accusations.
presidents can have migraines dana goldstein july 19, 2011

when the supreme court rules that anyone can say anything—often anonymously—with unlimited money, then they will.
race-baiting campaign proposed against obama revisits what we thought was past mark mckinnon may 16, 2012

in response, treasury anonymously accused barofsky of having “been consistently wrong about a lot of big things.”
jack lew and the obama administration’s finance-friendly status quo lloyd green february 18, 2013

or the person who anonymously left food for you outside your door.
ping fu’s journey from cultural revolution orphan to geomagic ceo katie baker january 19, 2013

as a result of this secrecy, russian servicemen are dying in ukraine anonymously, relatives in kastroma said.
kremlin is caught putting boots on the ground in ukraine anna nemtsova august 25, 2014

historical examples

and at last he put four sovereigns in an envelope and sent them to her anonymously by messenger.
the amazing interlude mary roberts rinehart

the author of this letter has, at my request, authorized me to publish it anonymously.
the s-xual question august forel

she consented finally to write fragments of her life, anonymously.
the log-cabin lady, an anonymous autobiography unknown

besides, i can send back everything in the morning, anonymously, by parcel-post.
n-body louis joseph vance

the truth is they came in anonymously, and i thought they were more likely to be accepted if i said i had written them.
happy days alan alexander milne

adjective
from or by a person, author, etc, whose name is unknown or withheld: an anonymous letter
having no known name
lacking individual characteristics; unexceptional
(often capital) denoting an organization which provides help to applicants who remain anonymous: alcoholics anonymous
adv.

1728, from anonymous + -ly (2).
adj.

c.1600, from late latin anonymus, from greek anonymos “without a name,” from an- “without” (see an- (1)) + onyma, æolic dialectal form of onoma “name” (see name (n.)).