Mushmouth American slang
Someone who does not or is unable to express their feelings or ideas clearly.
Whenever I don't have enough sleep, I become a mushmouth.
I felt so ashamed of myself for being a mushmouth.
If I hadn't been a mushmouth, I would have been chosen for that position.
This slang dates from the mid 19th century.
One needs to understand the basic techniques or primary details of something before taking actions that require greater skills
Peter failed because he did not learn to walk before he ran.