the.com/plunk

means To drop, place, or pay something down heavily and abruptly — with a flat, graceless thud instead of a smooth landing.

from Plunk is imitative — a word born from the sound itself, like plop or clunk. It surfaces in the 1800s meaning both the dull hollow noise of something dropping and the act of dropping it that way, and later stretched to 'plunk down money,' paying up bluntly and all at once. Its cousin 'plink' covers the same territory but lighter and tinnier; plunk is the heavier, duller thud of the two.