at the tip of one's tongue

[at the tip of one's tongue] or [on the tip of one's tongue] {adv.phr.} {informal} 1. Almost spoken; at the point of being said.

It was at the tip of my tongue to tell him, when the phone rang.

John had a rude answer on the tip of his tongue, but he remembered his manners just in time.

2. Almost remembered; at the point where one can almost say it but cannot because it is forgotten.

I have his name on the tip of my tongue.