IPA: //ʌnˈwɒntɪdli//
KK: /ʌnˈwoʊntɪdli/
In a way that is not usual or customary; unexpectedly.
She unwontedly agreed to go on the trip, surprising everyone.
Unwontedly → It is formed from "un-" (meaning not) and "wont" (from Old English "wunian", meaning to be accustomed or to dwell) and the suffix "-edly" (meaning in a manner). The word "unwontedly" means in a manner that is not accustomed or unusual.
Think of 'not accustomed' ('un-') and 'to dwell' ('wont') to remember that 'unwontedly' describes something done in an unusual manner.