The ell is a unit of length and originates from historic England and uses the symbol ell.
The ell usually measured 45in or 1.143m but was origally a "cubit" - which was the length from your elbow to the tip of your fingers and literally translated from the word "arm". It was mostly used in the tailoring world when buying and selling textiles.
Although now obsolete, the word "ell" still survives in the English word "elbow".
The parsec is a unit of length and is used in the Astronomical system of units. It is denoted by the symbol pc.
It is equal to 3.26156 ly (light years) which is approximately 31 trillion kilometres (19 trillion miles). It's used to measure huge distances to objects and planets outside of our Solar System.
It was first brought into use by Herbert Hall Turner (a British Astronomer) in 1913 and was invented to use in calculations of astronomical distances to make it easier in calculations using raw data.