on the tip of (your) tongue
about to be said.
Her name is right on the tip of my tongue — Helen something or other, what is her last name!
英语词组固定搭配大全包含18674条英汉双解词组，基本涵盖了全部常用英文词组、短语的翻译及用法，是英语学习的有利工具。