שִׁלְשׁוֹם shilshôwm (H8032)

trebly, i.e. (in time) day before yesterday

1) day before yesterday, three days ago 1a) an idiom for 'heretofore in times past'

or שִׁלְשֹׁם; from the same as שֶׁלֶשׁ (H8028);