to be desirous of speaking
悱 centers on the inner urge to speak but being unable to express oneself, a state of desiring to speak while feeling held back.
悱 combines 忄 (heart/mind) with 非, which likely contributes the sound and may suggest negation or opposition, together conveying a mind blocked from speaking.
The heart radical 忄 beside 非 (not, wrong) suggests a heart that cannot speak out: the mind wants to say something but feels it is not right to do so.
For ヒ, imagine a person who wants to speak but only manages a soft 'he...' sound, hesitating: 'he' cues ヒ, and the heart is full of unspoken words.