extensive, full, fill, complete
彌 centers on the idea of something spreading out to cover or fill a space completely: being extensive, full, or complete. The meanings of filling and completing are natural applications of this same expansive, all-encompassing quality.
彌 combines 弓 (bow) with 爾, which likely contributes the sound and may have originally suggested a bowstring stretched to its full extent, giving the idea of extensiveness and completeness. The exact historical development is uncertain.
The left side is a bow 弓, and the right side 爾 looks like a complex, spread-out structure. Imagine pulling a bowstring back until the bow is fully extended and the string fills the entire space—this is the idea of being extensive and complete.
For ミ, picture a bow 弓 stretched so far that it looks like the letter 'M'—the 'M' bow is fully extended, and 'M' cues ミ.