Most likely because they are the cells from which all specialised cells Stem, i.e. stem cells are the precursors which form more differentiated types of cells, e.g. blood, bone are formed from, or...
Stem cells are cells that have the potential to develop into a variety of different cells e.g skin cells, nerve cells, blood cells etc. The word stem in "stell cell" is best pictured as the stem of a...