block on (something)
To suddenly forget or be unable to recall something. I can't believe I totally blocked on her name earlier when I've known her for years!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
To forget or fail to remember something; have a mental block about something: I had met these people before, but this time I blocked on their names.
The American Heritage® Dictionary of Phrasal Verbs. Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.