Love or infatuation of very young persons; calf love(1834+)
Idioms and Phrases with puppy love
puppy love
Also, calf love. Adolescent love or infatuation, especially one that is not expected to last, as in Beth is besotted with him, but we think it's just puppy love, or He's got a bad case of calf love. [ First half of 1800s ]