pickthank
/ˈpɪkθaŋk/(also peckthank) Now archaic and literary
noun
A person who curries favour with another, especially by informing against someone else; a flatterer, a sycophant; a telltale.
adjective
Of, characteristic of, or designating a pickthank; flattering, sycophantic; talebearing.
Origin
Late Middle English. From pick- + thank, after to pick a thank.