Treibsand.

From Middle High German tripsant, trybsand (both Central German, 14th c.). Like all High German attestations before the 16th century, these seem to be equivalent to modern Trieb + Sand, which is notable because Middle High German trip was commonly used of the driving of livestock only. Hence, possibly from Middle Low German drifsant (15th c., could be drīfsant), dryffsandt (16th c.), from *driftsant (compare unambiguous Dutch drifsant, driftzant, 16th c.). A borrowing from Low German may also be corroborated by the semantic context, though neither silt nor quicksand are restricted to seashores. The modern form with -ei- by adaptation to underlying treiben (also in contemporary Dutch drijfzand, Low German Driefsand).