5th century AD. Many view plough as a derivative of the verb *plehan ~ *plegan 'to take responsibility' (cf. German pflegen 'to look after, nurse'), which would explain, for example, Old High German pfluog with its double meaning of 'plough' and 'livelihood'. Guus Kroonen (2013) proposes a vṛddhi-derivative of *plag/kkōn 'sod' (cf. Dutch plag 'sod', Old Norse plagg 'cloth', Middle High German 'rag, patch, stain'). Finally, Vladimir Orel (2003) tentatively attaches plough to a PIE stem *, which supposedly gave Old Armenian "to dig" and Welsh "crack", though the word may not be of Indo-European origin. Parts The basic parts of the modern plough are: beam hitch (British English: hake) vertical regulator coulter (knife coulter pictured, but disk coulter common) chisel (foreshare) share (mainshare) mouldboard Other parts include the frog (or frame), runner, landside, shin, trashboard, and stilts (handles). On modern ploughs and some older ploughs, the mould board is separate from the share and runner, so these parts can be replaced without replacing the mould board. Abrasion eventually wears out all parts of a plough that come into contact with the soil. History Hoeing When agriculture was first developed, soil was turned using simple hand-held digging sticks and hoes. These were used in highly fertile areas, such as the banks of the Nile, where the annual flood rejuvenates the soil, to create drills (furrows) in which to plant seeds. Digging sticks, hoes and mattocks were not invented in any one place, and hoe cultivation must have been common everywhere agriculture was practised. Hoe-farming is the traditional tillage method in tropical or sub-tropical regions, which are marked by stony soils, steep slope gradients, predominant root crops, and coarse grains grown at wide intervals. While hoe-agriculture is best suited to these regions, it is used in some fashion everywhere. Ard Some ancient hoes, like the Egyptian mr, were pointed and strong enough to clear rocky soil and make seed drills, which is why they are called hand-ards. However, domestication of oxen in Mesopotamia and the Indus Valley Civilisation, perhaps as early as the 6th millennium BC, provided mankind with the draft power needed to develop the larger, animal-drawn true ard (or scratch plough). The earliest surviving evidence of ploughing has been dated to 3500–3800 BCE, on a site in Bubeneč, Czech Republic. A ploughed field, from c.2800 BCE, was also discovered at Kalibangan, India. A terracotta model of the early ards