1
general::
Phrase(s): stop up
[for something] to become clogged. • The sink stopped up again!, Phrase(s): stop something up (with something)
to plug or clog something with something. • Gary stopped the sink up with bacon grease. • He stopped up the sink with bacon grease. • Try not to stop the sink up.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Fill a hole or gap, block an opening or passage. For example, We need to stop up the chinks in the walls, or The sink is stopped up; it won't drain. This idiom was at first put simply as stop, the adverb up being added only in the early 1700s.
American Heritage Idioms