put a bug in (one's) ear
To speak to one in order to impart some particular information, suggestion, hint, or warning. I've been putting a bug in his ear for months about what I wanted for my birthday, but he was totally clueless when the day came. They weren't listening to me, so I asked my boss to put a word in their ear about the importance of meeting this deadline.
put a bug in someone's ear
Give someone a hint about something, as in Janet put a bug in her husband's ear about getting the children a dog for Christmas. This idiom presumably likens the buzzing about of an insect to a hint, although the exact analogy is not clear. [c. 1900]
put a bug in (someone's) ear
Informal To impart useful information to (another) in a subtle, discreet way.