IPA: //ˌʌnəˈsjuːmɪŋnəs//
KK: /ʌnəˈsjuːmɪŋnəs/
A quality of being modest and not drawing attention to oneself; being simple and natural.
Her unassumingness made her very approachable and easy to talk to.
Unassumingness → It is formed from "un-" (meaning not), "assuming" (from Latin "assumere", meaning to take up or adopt), and "-ness" (meaning the state or quality of). The word describes the quality of not taking up or adopting an arrogant or presumptuous attitude.
Think of 'not' ('un-') being combined with 'taking up' ('assumere') an arrogant attitude, which helps you remember that 'unassumingness' means the quality of being modest or humble.