The internal cubic capacity of a vessel expressed in "tons" taken at 100 cubic feet each. Historically the word originates from the centuries after the Norman conquest when trading ships carried huge cargoes of wine in casks called "Tuns" whose capacity was fixed by law at not less than 252 gallons. Port and harbour duties were based on the number of such "tuns" a ship could carry and hence the term "tonnage" which later became "tonnage". Earliest records in the UK referring to tonnage date back from 1422 when it was decreed that keels carrying coal at Newcastle should be measured and marked.
Ubungakanani bekhyubhu yangaphantsi kwenqanawe buboniswe "ngeetoni" ezithatyathwe kwiikyubhu ezingama-100 emilinganiselo yenyawo ngalinye.