means To keep something going over time — to support, nourish, or hold it up so it doesn't collapse or fade; also, to undergo or endure (as in sustaining an injury).

from From Latin 'sustinere,' a marriage of 'sub-' (up, from below) and 'tenere' (to hold) — literally 'to hold up from underneath.' It traveled through Old French 'sustenir' into English, carrying that image of something propped, braced, kept aloft. Its cousin 'tenere' is a busy root, also lurking inside 'tenant,' 'tenacious,' and 'contain' — all words about holding fast.