From The book of Christmas: descriptive of the customs, ceremonies, traditions ... By Thomas Kibble Hervey (1845)
This day—which, in our calendar, is still dedicated to the first Christian martyr, St. Stephen (for John the Baptist perished in the same cause, before the consummation of the old law, and the full introduction of the Christian dispensation),—is more popularly known by the title of Boxing-day; and its importance, amongst the Christmas festivities, is derived from the practice whence that title comes.
We have already mentioned that the custom of bestowing gifts, at seasons of joyous commemoration, has been a form of thankfulness at most periods;—and that it may have been directly borrowed, by the Christian worshippers, from the Polytheists of Rome, along with those other modes of celebration which descended to the Christmas festival, from that source,—introduced, however, amongst our own observances, under scripture sanctions, drawn both from the Old and New Testaments. The particular form of that practice, whose donations are known by the title of Christmas-boxes (and which appear to differ from New-year's gifts in this,—that the former, passing from the rich to the poor, and from the master to his dependants, are not reciprocal in their distribution,—whereas the latter are those gifts, for the mutual expression of good-will and congratulation, which are exchanged between friends and acquaintances), was, perhaps, originally one of the observances of Christmas-day, and made a portion of its charities. The multiplied business of that festival, however, probably caused it to be postponed till the day following,—and thereby placed the Christmas-boxes under the patronage of St. Stephen.
The title itself has been derived, by some, from the box which was kept on board of every vessel that sailed upon a distant voyage, for the reception of donations to the priest; who, in return, was expected to offer masses for the safety of the expedition, to the particular saint having charge of the ship—and, above all, of the box. This box was not to be opened till the return of the vessel; and we can conceive that, in cases where the mariners had had a perilous time of it, this casket would be found to enclose a tolerable offering. Probably the state of the box might be as good an evidence as the log-book, of the character of the voyage which had been achieved. The mass was, at that time, called Christmass;—and the boxes kept to pay for it were, of course, called Christmass-boxes. The poor, amongst those who had an interest in the fate of these ships,—or of those who sailed in them,—were in the habit of begging money from the rich, that they might contribute to the mass boxes; and hence the title which has descended to our day:—giving to the anniversary of St. Stephen's martyrdom the title of Christmas-boxing day— and, by corruption, its present popular one of Boxing-day. A relic of these ancient boxes yet exists, in the earthen or wooden box, with a slit in it, which still bears the same name; and is carried, by servants and children, for the purpose of gathering money, at this season—being broken only when the period of collection is supposed to be over.