The expression "to butter someone up" means to give someone exaggerated or flattering praise, often with the intention of gaining an advantage or achieving something. It usually involves flattery or insincere praise in order to win the person's favor.
To butter someone up
For example, you might say, "He buttered up the boss so much that he got the promotion even though other employees were better qualified." or "You don't need to butter me up, I know you just want my help."

The origin of the phrase probably lies in medieval customs. In the past, honey was actually used to treat wounds in the mouth or to attract and calm animals. This medical use of honey, which is an antiseptic and has a soothing effect, may have given the phrase its figurative meaning.
At the same time, honey symbolizes sweetness and thus a sweet, pleasant feeling that is evoked by flattery.
Another theory is that it is a blended version of two related phrases: "to give someone honey" (to give something sweet and pleasant) and "to butter someone up" (to praise or bribe someone excessively).
Comparison with similar phrases in other languages
Similar to the German expression, the English expression "To butter someone up" means to flatter someone or to give them exaggerated praise in order to gain an advantage. "He's just buttering up his boss to get that promotion."
The French phrase "Passer de la pommade" means to give someone flattery or exaggerated praise, often with an intention based on self-enrichment. "Il n'arrête pas de lui passer de la pommade pour obtenir sa faveur."
Literally translated, the Spanish expression “Dorar la píldora” means “to gild the pill” and describes the act of beautifying an unpleasant or bitter fact, often through flattery or lies. “Le está dorando la píldora para que no se enoje con la decisión.”
The phrase "to butter someone up" probably has its origins in historical practices of the medicinal use of honey and the symbolic meaning of sweetness. In its current use, it is used to describe insincere flattery or exaggerated praise. A comparison with other languages shows that the idea of flattery and gaining favor is universal, even if the imagery varies.