(now chiefly dialectal) Used to form adjectives expressing resemblance or likeness to, similar to -like. · (plural -kin) Used to form nouns having qualities of or belonging to a particular kind, class, or sort.
From Dutch boomken (“shrub, little tree”), equivalent to boom + -kin. Note that the English word boom is etymologically related to the aforementioned in the sense of "large stem", or "big tree". Compare German Baumke, Bäumchen.