大いに
おおいに · ooini · JLPT N3 · adverb
much
大 = big, so 大いに means in a big way: greatly, very much
大 (おお) is the native Japanese reading of big, as in 大きい. Adding に turns it into an adverb, in a big way. It sounds like oh, oh, eeny: two big ohs for a big amount. It often goes with verbs: 大いに楽しむ means to enjoy greatly.
大 — pictograph of a person with arms outstretched
大 is a pictograph showing a person standing with arms and legs spread wide. The outstretched arms suggest 'big' or 'great', extending from the literal image of a large stance to abstract meanings like important or grand. It is one of the oldest characters, found on oracle bones.