Why doesn't 虛 contradict 謙虛? Definition D for 虛 lists &quot;vainly&quot;. Unquestionably, &quot;vainly&quot; is the opposite of &quot;modesty&quot;.
And &quot;modesty&quot; implies that you possess something valuable, like knowledge or wealth, but you keep it to yourself. A modest person isn't &quot;empty&quot; or &quot;vain&quot;! I don't understand how 虛 fits 謙虛.

Above is Oxford Chinese Dictionary (2010) p 577. Below is op. cit. p 845.
虛 = empty, the opposite of 虛(empty) is 實 (solid)
虛 in 謙虛 refers to 虛心 (empty heart = open mind)
A cup full of water cannot take in new water
A mind full of preconceptions cannot take in new ideas
謙虛 = modest, humble, and open-minded (willing to listen and learn)
Also, look at my answer to this question
What does 虚怀若谷 mean?