_Tu Autem_ (Vol. iii., p. 265).--The words "Tu autem, Domine, miserere
nostri," "But Thou, O Lord! have mercy upon us," were originally a form of
prayer used by the preacher at the end of his discourse, as a supplication
for pardon for any sinful pride or vainglory, into which he might have been
betrayed in addressing his congregation. Hence the words "tu autem," as
Pegge properly says, came to denote a hint to the reader to leave off.
The custom is still in constant use among the members of the cathedral
church of Durham. At the public dinners given by the canons, in what is
there called "hospitality residence," one of the choristers comes in after
dinner, dressed in his official costume, and, taking his station behind the
canon in residence, reads, in the manner which is now well known as
_intoning_, eight verses of the 119th Psalm, first saying, "Here beginneth
the ---- part of the 119th Psalm."
When the eight verses are concluded, the canon turns round to the
chorister, saying "tu autem," giving him a shilling; to which the chorister
replies, "Domine miserere nostri," and retires.
The explanation of the words, as originally employed, is given by Rupertus
_De Divinis Officiis_, lib. i. c. xiv.: