This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
悥 combines 言 (speech) and 心 (heart/mind), but its exact historical development and original meaning are uncertain.
Words 言 resting on the heart 心 could suggest unspoken thoughts or a full heart, but the true meaning is unclear.
For オク, imagine an oak tree with words carved into its heartwood: oak -> オク, and the tree holds the words deep inside.