"Stem and leaf" name origin

The name came off the shape: the “stem” has the largest place-value digits on the left and the “leaf” with one single digit on the right.

Stem and leaf plot vs. histogram

The type of chart is quite similar to an older colleague - the histogram. They both allow comparing data, but the stem and leaf plot can showcase individual data points, which a histogram cannot do.

The origin of stem-leaf plots

Stem-leaf plots' origins go back to the beginning of the XX century. Still, their popularity blossomed in the early 80,  after John Tukey's book on exploratory data analysis in 1977, and was based on monospaced fonts. Typewriter type styles allowed computer technology of the time to generate these graphics formats easily. Modern technology made these techniques less common.