"I'll Tell You a Secret Later"

R says this to us all the time.

When I'm dropping her off at day care, she pulls me close and whispers very conspiratorially, "Mommy, mommy, mommy . . . I'll tell you a secret. Later. Kay."

When I'm putting her to sleep and saying goodnight, she'll say, "I want Daddy to tell me a secret later." I always tell her he will. She's never once asked for the secret, though.

Sometimes when she's playing, she'll run up to me and say, "I'll be right back. I'm gonna tell you a secret later."

What do you think it all means??