矣

Glyph origin
. may also act as a phonetic component.

Etymology 1
tentatively suggests a connection to adverb, drawing a parallel with the 了₁ (perfective particle) and 了₂ (change of state modal particle) meanings of , but doubts that they are etymologically related, suggesting the connection may be purely semantic and for aspectual functions.

Kanji

 * 1) kanbun (Literary Chinese) sentence particle