丸々
まるまる · marumaru · JLPT N1 · na-adj
completely
maru maru = round + round: a whole circle, so nothing is left out, i.e. completely
The word doubles 丸 (maru, round or circle), like saying a thing is round and round. Something fully round has no edges missing, which is how 'completely' came to mean whole and entire.
丸 — 九 nine + dot 丶
Originally a pictograph showing a small round object or pellet, depicting something that can be rolled. The modern form resembles 九 with a dot, but historically it derives from 仄 inverted, suggesting something tipping or rolling. It came to mean 'round ball,' 'pellet,' or 'pill.'