What does "butter up" mean?

English as a Second Language English Teacher Explanations (ESL Tests)
1

English Language Tests, Intermediate level

ESL/EFL Test #166 [color=blue]“Phrasal Verbs (B to C)”, question 5

Ken tried to … his teachers in order to get a good report card.

(a) butter up
(b) butter over
(c) butter in

English Language Tests, Intermediate level

ESL/EFL Test #166 [color=blue]“Phrasal Verbs (B to C)”, answer 5

Ken tried to butter up his teachers in order to get a good report card.

Correct answer: (a) butter up

Your answer was: [color=green]correct
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What does “butter up” means in this sentence?

2

He did everything he could to win his teacher’s approval. Went messages. Made coffee. Carried their books etc,.

3

Is it something like to ingratiate with someone,to fawn, slaver?