I am not too sure but "whispering sweet nothings" to me is when he whispers anything in my ear and it tickles! Teeheehee!
Where did the term " sweet nothings " originate from?
Apparently it was from an 1876 poem by Mary Elizabeth Braddon:
"As low he bends o'er her he loves so dear,
To whisper some sweet nothing in her ear."