[Avodah] barukh sheamar

[Eli Turkel]

<<Kaddish yasom based on a dead person's message to R Akiva.

* Being careful not to speak during Vayechulu and the Bracha Me'ein Sheva,
 based on a message a dead person gave to someone in a dream.

* Not davening "achorei beis haknesses" without turning ones face to it
(I'm really not sure what exactly this means), based on giluy Eliyahu.>>

R. Akiva never mention any kaddish yatom, that is a much later minhag
for some of the origins see for example
http://www.oztorah.com/2010/04/mourners-kaddish-ask-the-rabbi/

None of this material suggests a link with mourning, but Rabbi DS
Telsner, in his “The Kaddish - Its History and Significance” (ed. GA
Sivan, Jerusalem, 1995) puts forward the idea that the development of
the mourner’s version of the Kaddish may have come about as the result
of a shift in emphasis. At first the Kaddish honoured the living (“in
your life and in your days”). During the medieval persecutions it
consoled the survivors of the catastrophes and implied that they
should not let their tragic experiences weaken their faith in
redemption. Eventually it memorialised those who had lost their lives,
and so it became a prayer for the dead rather than the living.

This theory reflects the fact that the Mourner’s Kaddish probably
arose in north-west and central Europe in the Middle Ages. Another
medieval source, the Machzor Vitry, speaks of a mourner conducting the
service on Saturday night, probably because of the belief that at the
end of Shabbat the dead are selected either for punishment or for
reward. Eventually the mourners recited Kaddish without necessarily
conducting the service, and finally Kaddish at the end of the service
became the mourner’s prerogative. This is often linked to a tale about
Rabbi Akiva which suggests that a person’s son can redeem the parent
from torment by saying Kaddish (Kallah Rabbati, ch. 2, etc.)

<<We start with the tradition that there was a piece of paper.  That's not
a stretch, that's what the Or Zarua says.>>

from wikipedia

Initially, Saadya Gaon instituted the recitation of barukh she'amar
for Shabbat, but in France, it became a custom to recite this prayer
daily.

in other posts on the web

Until the fourteenth century, most rabbinic discussions of its origins
assumed the existence of some vague rabbinic enactment, the exact
nature of which was of no great concern. The Tur mentions in passing
that the blessing appears in Sefer Heikhalot. R. David ben Yehudah
Hasid, in his influential kabbalistic prayer commentary, Or Zarua,
states that barukh she-amar was not established by the men of the
Great Assembly. Instead, scholars and men of wisdom received it
directly from “the tradition of the covenant” when a note fell from
heaven. R. David was no doubt rebutting a theory suggested by some
unidentified group or person in his world. Obviously, it was not a
mainstream theory, judging from the literature of the period. However,
in the sixteenth century, R. Meir ibn Gabbai, in his commentary Sefer
Tolaat Yaakov, miscites the Or Zarua, stating that it ascribes barukh
she-amar specifically to the men of the Great Assembly, who
established the prayer on the basis of a note that fell from heaven.
This clever ascription removed all doubt about the legitimate origins
of barukh she-amar by placing its provenance in the same mythical
pre-talmudic antiquity as the amidah, the paradigmatic Jewish prayer.
This explanation eventually became standard in noncritical prayer
commentaries.
The impetus to generate and accept such “origins” for this single
prayer must have come from the continuing need to justify its
recitation. Before Ibn Gabbai’s solution was widely accepted, Hizkiah
da Silva, in his Peri Hadash, a late seventeenth-century Sefardi
commentary on the Shulhan Arukh, challenged the geonic right to
establish new blessings, basing his argument on the Rosh’s objections
to the priest’s blessing at the pidyon haben. Da Silva was either
unaware of, or, more likely, unconvinced by the eighteenth-century
commentators, the Peri Megadim and the Beer Heitev. The Beer Heitev,
like his Sefardi contemporary, the Hida, also points to the Tur’s
identification of the source of the blessing in the Sefer Heikhalot as
proof of its pre-talmudic origins

-- 
Eli Turkel