A cargo is just something - precious or not - being carried, generally on a boat or aircraft. However, nowadays, the phrase 'precious cargo' is frequently used to mean an unborn baby. In other words, it's a sort of joke in which the child is seen as a 'load' that the mother-to-be has to carry. She must, of course, be very careful about it, in the same way that a shipment of diamonds would probably be accompanied by armed guards.
i think it had something to do with tea or spice coming to the uk in the old tea clippers.i also heard it related to royalty when they travelled on ships in the old days.king james 1st of britain his queen travelled from denmark and her boat nearly sank,i believe old james was a part of the life saving group.it happen off coast of scotland.these are some of the reasons.also royalty or the offspring in line to the throne are not to travel 2gether,incase they all go down 2gether
�Precious Cargo: California Indian Cradle Baskets and Childbirth Traditions� presents cradle baskets in their cultural context through direct collaboration with contemporary California Indian weavers. �Precious Cargo� examines traditional beliefs and practices concerning childbirth and the use of cradle baskets, both historically and contemporarily, among Pomo and Western Mono peoples, with additional material from 28 other tribal regions throughout the state.