The phrase "putting a bug in one ear" means to remind someone or suggest something to them. There are several synonyms for this phrase including "planting a seed," "dropping a hint," "whispering in their ear," and "suggesting gently." All of these phrases convey a similar meaning and intention to the original phrase. These synonyms are commonly used in casual and professional settings to convey a message or idea to someone without being too direct or forceful. Using these alternative phrases can help to communicate a message in a subtle and effective way, while also demonstrating good communication skills and tact.