an indefinitely great length or
period of
time; practically never. The
origin of this
phrase is uncertain though it may come from the
fact that in older
times (the 1800s, when this
phrase originated), Sundays were days where, for a "well-brought up" person, no games were played and no flippancy was allowed. For one who was very spirited (like a young person or child) these days seemed to
drag out and go on forever. Thus a month of Sundays (thirty of them) would truly be a long
time for such a person.