ASHAMNU (Heb. אָשַׁמְנוּ; "we have trespassed" or "we are guilty"), opening word and hence the name of a formula of confession of sins which forms part of the *Day of Atonement and of other penitential services, such as *seliḥot, the daily morning and afternoon prayers (according to most Sephardi and some Ashkenazi rites), and the prayer service recited on the day preceding the New Moon (tefillat *Yom Kippur Katan) according to the Ashkenazi rite. Its origin is in the confession recited by the high priest on the Day of Atonement (see Avodah). In later periods it was expanded in the more elaborate medieval style. The Ashamnu confession lists trespasses of a moral nature only and consists of 24 or more words in alphabetical order, the last letter of the Hebrew alphabet being repeated three times. In the Reform ritual Ashamnu appears in an abridged form. Ashamnu is also used as the form of confession at the approach of death as well as by the bridegroom and bride before their wedding, that day being considered a sort of "day of Atonement" for them (Shab. 32a; Sanh. 6:2; 43b).
Elbogen, Gottesdienst, 149–51, 229.