pile up
蘊 centers on accumulation: things piling up or being stored in a concentrated, often hidden, way. The single given meaning 'pile up' is the core idea.
蘊 combines 艹 (grass) with 縕, which likely contributes the sound and the idea of tangled fibers or accumulation. The overall sense is things piling up like matted grass or stored goods.
The grass top 艹 covers a dense, tangled lower part 縕, like a pile of matted vegetation. Picture a heap of grass and fibers accumulating into a mound.
For ウン, imagine a huge pile of wool (ウール, ūru) accumulating: the 'un' in wool (ウ) cues ウン, and the pile grows higher.
great erudition; extensive knowledge; vast stock of knowledge
bardo; state (or period) of intermediate existence between one's death and rebirth (in Japan, 49 days)
the five skandhas (matter, sensation, perception, mental formations and consciousness); the five aggregates
inexhaustible supply
perception
inner mysteries (of a field of study); secrets
to master the secrets of
to draw upon one's profound knowledge
formation of volition; aggregate of volition