From Latin 'calcare' (to tread/press), from 'calx' (heel)—caulking was originally trampling sealant into ship seams.
To seal the seams of a boat or gaps in construction with a waterproof filler to prevent leaking.
From Old North French 'cauquer' (to press, to trample), from Latin 'calcare' (to tread, to press with the heel), from 'calx' (heel). Caulking originally involved trampling oakum (tarred fiber) into ship seams with a mallet and iron, pressing it tight. Key roots: calx (Latin: "heel").