only, merely
秪 centers on limitation to a single thing: only or merely. It expresses that something is just that and nothing more.
秪 combines 禾 (grain) with 氐, which likely contributes the sound. The exact historical development is uncertain, but the character is used to express 'only' or 'merely'.
Picture a single stalk of grain (禾) standing alone in a field, with nothing else around it. That one grain is the only thing there—merely that and nothing more.
For チ, imagine a single grain of rice being the only food on a tiny plate: the word 'tiny' sounds like チ, and it emphasizes that there is merely one grain.