The slash on our keyboards is a virgule. The name comes down to us from Latin through French (virgula “twig”). It served medieval European literature as a comma and still does this in English language poetry. It also separates things (2015/2016), and it stands in for “or” (as in and/or) and “per” (as in feet/second). We also use it to build level fractions (1/3).
The solidus is slightly thinner and more oblique. Typographers use it to improvise fractions (see illustration). Solidus was the name of a Roman coin, and a Roman pound (libra) was comprised of 72 solidi. The British pound mark (£) is a descendant of the Roman libra. The symbol for the British pound sterling a stylized italic upper case L. It’s an abbreviated form of libra, “scale/balance.” The Latin pondo for “pound” was about twelve ounces, and libra is the source of the abbreviation “lb.” The English shilling is abbreviated with a solidus (e.g. “1 ⁄ 6” would be 1 shilling and sixpence).
While we’re on currency symbols, the dollar comes to us from the Spanish peso. A handwritten “Ps” was an abbreviation for pesos in the New World. As time went on, the abbreviation was written with the S on top of the P. In English, it was first recorded in the 1770s in manuscripts and is seen in print in the early nineteenth century.
Again, a tip of the sombrero to the brilliant Humez brothers.