Better keep still about it
(someone had) better keep still about it
(Someone had) better not say anything about a particular issue or situation. "Someone" can be used in the phrase itself, especially when the listener already knows who the speaker is talking about. A: "I think Jake knows that we doctored the numbers in that report." B: "Well, someone had better keep still about it then." Better keep still about it so that the boss doesn't suspect anything.
Better keep still about it.and Someone had better keep still about it.; Better keep quiet about it.; Someone better keep quiet about it.
A particular person ought not to tell about or discuss something. (The someone can stand for any person's name, any pronoun, or even the word someone meaning "you-know-who." If there is no Someone had, the phrase is a mild admonition to keep quiet about something.) Mary: I saw you with Bill last night. Jane: You'd better keep quiet about it. Jane: Tom found out what you're giving Sally for her birthday. Bill: He had better keep quiet about it!