1
general::
Advance slowly or stealthily, as in The cat crept up on the bird, or Autumn is creeping up on us. This expression is recorded in slightly different form?? creep in or creep onfrom the 15th century on. One of the Hymns to the Virgin and Christ (c. 1430) has ‘‘Now age has cropen [crept] up on me ful stille."
American Heritage Idioms
2
general::
Phrase(s): creep up on someone or something
to sneak up on someone or something. • Please don’t creep up on me like that. You scared me to death. • The cat crept up on the mouse. *the creeps and *the willies a state of anxiety or uneasiness. (*Typically: get ~; have ~; give someone ~.) • I get the creeps when I see that old house. • I really had the willies when I went down into the dark basement.
McGrawhill's American Idioms And Phrasal Verbs