(See second quotation.) Canting use of the word.

1

1851.  What seemed to be their annual reappearance at the altar.—S. Judd, ‘Margaret,’ i. 151.

2

1874.  Goodwin immediately invited the penitents into the enclosed pen-like place called the altar, and the whole space was filled with kneeling mourners, whose cries and groans made the woods resound.—E. Eggleston, ‘The Circuit Rider,’ p. 261.

3