到 builds on 至, which pictured an arrow landing point-down in the ground — the very image of arrival. The knife radical 刂 was added for sound. An arrow strikes earth: you have arrived.
到 is how Chinese marks completion of movement: 到了 ('arrived!' — the two syllables every taxi ride ends with), 到家 (reach home), 迟到 (arrive late — the schoolchild's dread). As a verb-complement it means an action truly landed: 看到 (see — and register), 买到 (manage to buy), 找到 (find). Roll call in Chinese classrooms is answered with a single crisp 到! — present, arrived, here.
An arrow 至 stuck in the ground, sharp as a knife 刂 — ARRIVED.
Chinese students answer roll call with 到! ('arrived') — one syllable doing the work of 'present, sir'.