be nuts about (someone or something)
1. To be very passionate and enthusiastic about something. My daughter is nuts about sports—she's currently playing soccer and tennis and taking swim lessons.
2. To be very romantically interested in or in love with someone. I've seen the way Tim smiles at you—that guy is nuts about you!
nuts about, be
Be extremely enthusiastic; also, be extremely fond of. For example, Ellen is nuts about opera, or Kevin has been nuts about Megan since he met her. This seemingly new slangy expression began life in the late 1700s as nuts on or upon; about began to be substituted about 1940.