The starting point of this paper is the problem of identity, origin and migration of the Amorites. The earliest attestation of “Amorites” is Sumerian compound MAR.TU, which first appeared in the texts dating to about 2500 BC. This article concentrates on this Sumerian combination for which we still do not know how to pronounce it nor what it originally meant. I analyzed a corpus of protocuneiform texts and tried to identify within it the meaning of the symbol MAR. After examining 138 tablets (from Uruk, Umma, Larsa, Jemdet Nasr, Kish and Uqair) on which the MAR symbol (112 administrative and 26 lexical) was written, I concluded that the MAR symbol represented a thing or an idea that was in Uruk III phase important for the parts of the economy organized and supervised by the institutions located in the centers in vicinity (Uma, Larsa, Ukair) or more remote areas (Jemdet Nasr, Kish) of Uruk. In the Umma it was associated with sheep, in Larsa with barley and in Jemdet Nasri with the sale (or purchase) within the sheep industry. If we consider such an interpretation, then the symbol MAR, idea or thing behind this symbol, was part of the activities that were not directly related to the “central administration” in the city of Uruk. The MAR symbol is essentially a GA2 symbol (“storage, container”?) with an additional notch. Since the symbol is relatively rarely written, we should take into account the landscape in which recorded operations took place, where the primary means of transport was a boat or a ship. However, in certain season and for the needs of certain activities, wagons were also used (during low waters). One of the more common contexts in which the MAR symbol is written is that of operations with the KIS symbol. It was already suggested that it represent a wild donkey species as suggested by the iconography of the symbol itself. Two different variations of the symbols could indicate two different types of wild donkey and the variant most commonly found in protocuneiform texts may indicate a mix of domestic and wild donkey whose presence and exclusive status has been confirmed in recent years at sites in Syria, southern and northern Mesopotamia. There are no confirmations for the presence of such animals in the Uruk economy or any indication about their value in society. However, presence of the Uruk culture in the area thought to be a center of trade with wild donkeys in the 3rd millennium BC was confirmed some time ago. That is also the area of the supposed Amorite homeland, so the tradesmen of Uruk had to meet the indigenous people that scholars associate with the Amorites. Considering the results of all this analyzes, I believe that the backbone of the original meaning of MAR was the thing/idea “wagon/wagon transport”, what is also one of the later Sumerian meanings of the symbol MAR (“wagon”, “rush”) To this concept in the mid-3rd millennium BC symbol TU was added, for designation of a particular place or people. The TU symbol may have been just a phonetic supplement. MAR.TU could designate a collective name for all areas (which were of commercial interest) that had to be reached by wagons, but it could also denote all people who travel on wagons when flood water began to decline (when it was possible to enter southern Mesopotamia). In that case, the original MAR.TU should be translated simply as “migrants” without a specific specification about their homeland or ethnicity or any other affiliation.