The word "犯嘀咕" is formed by combining the verb "犯", meaning to commit or indulge in an action, with the onomatopoeic term "嘀咕", which mimics the sound of muttering and conveys a sense of whispering or doubting. Together, "犯" acts upon "嘀咕" to create a phrase that literally means "to commit muttering" and figuratively describes the act of harboring doubts or feeling uneasy.