蓄 appears in many common compounds: 储蓄 (savings), 蓄意 (premeditated/deliberate), 蓄电池 (rechargeable battery), 蓄水池 (water tank/reservoir), 含蓄 (reserved/implicit). The core meaning is always about accumulating or holding something inside.
The grass top hints at the original sense of laying up fodder — storing dried plants for animals through winter. From this storehouse-of-grass image the meaning generalises to saving up money, growing a beard, or harbouring thoughts.
Supplies the sound xù with no tonal change. It also reinforces the meaning, since 畜 itself denotes raising animals and accumulating reserves — a rare case where the phonetic and the semantic line up neatly.
