An Etymological Dictionary of the German Language/Lab
Lab, n., rennet,’ from MidHG. lap(d), n., ‘rennet,’ also ‘acid fluid,’ OHG. lab, ‘broth’; it is not improbable, since the latter is the prim. meaning, that the word is further cognate with OTeut. terms for ‘medicine.’ Goth. lubja, f., ‘poison,’ AS. lyb, ‘poison,’ OIc. lyf, ‘medicine, OHG. luppi, n., ‘deadly juice.’ Note specially MidHG. kœseluppe, f., OHG. châsiluppa, AS. cŷs-lyb, equiv. to MidHG. kœ̂se-lap. The way in which Lab is related by gradation to lubja corresponds perhaps to that of HG. Nase to AS. nosu, E. nose. The prim. meaning of the stem seems to be ‘strong, sharp perfume; plant juice’; OIc. lyf, ‘medicine,’ and Goth. lubja, ‘poison,’ are differentiations of the same orig. sense.