垫底

to put sth on the bottom / to eat sth to tide oneself over until mealtime / to lay the foundation / to come last in the rankings

pad / cushion / mat / to pad out / to fill a gap / to pay for sb / to advance (money)

(equivalent to 的 as possessive particle)

background / bottom / base / end (of the month, year etc) / remnants / (math.) radix / base