be on the tip of your tongue
be on the tip of (one's) tongue
To be close to being remembered, as if one is nearly about to say the thing trying to be recalled. Her name is on the tip of my tongue. Just give me a minute, I'll remember it.
be on the tip of your tongue1 be almost but not quite able to bring a particular word or name to mind. 2 be about to utter a comment or question but then think better of it.
1977 Bernard MacLaverty Between Two Shores It was on the tip of his tongue to ask her but he didn't have the courage.