These are difficult concepts to fathom, especially by Westerners. But Asians (especially Chinese and Indo-Chinese folks) should understand.
Belittling and undercutting one's personal exaltation and being in close touch with practical reality in behavior (which is the opposite of being boastful and vain) is what constitutes humility to me. These concepts have their roots in the
Mahaprajnaparamita Sutra (摩訶般若波羅蜜多經). Which is a very influential Mahayana text that is central to the formation of the Bengali psyche. The original text for this was written in Pali, which was a predecessor to our language Bengali (as well as spread later to most modern Indo-Chinese languages such as Burmese, Thai, Lao and Cambodian).
There is little parallel to these philosophies in other areas further West of us, as evidenced in PDF, even today. But I hold out hope that one day they shall see the light.