Resonant
Etymology
From Latin "resonare" (to resound), from re- (back, again) and "sonare" (to sound), from "sonus" (sound). It began strictly acoustic — describing echoing or reverberating sound — and grew a figurative sense: an idea or image that "sounds again" in the mind, striking a chord well after it is first heard.
adjective · /REZ-uh-nuhnt/
Deep and reverberating in sound, or rich in evoked meaning and association.
What it names
Anything that keeps sounding after the first strike — a voice, a phrase, or an idea that gathers force by echoing.
Example
Her closing line was so resonant that people were still quoting it back to her weeks later.
Related idea
Something poignant pierces you sharply and at once; something resonant keeps sounding — it lingers and accumulates meaning by echo.