Where did the term "broadcasting" come from?
It originally derived from Yorick, an older array-focused programming language that many of the original NumPy (née Numeric) designers were familiar with.
https://mail.python.org/pipermail/matrix-sig/1995-November/000143.html
http://dhmunro.github.io/yorick-doc/manual/yorick_50.html#Broadcasting
According to online Etymology:
1767, adjective, in reference to the spreading of seed, from broad (adj.) + past participle of cast (v.). Figurative use is recorded from 1785. Modern media use began with radio (1922, adjective and noun). As a verb, recorded from 1813 in an agricultural sense, 1829 in a figurative sense, 1921 in reference to radio.
Sometime later, definitions like this came about:
In telecommunication and information theory, broadcasting refers to a method of transferring a message to all recipients simultaneously.
The definition, for Numpy, builds on the above:
The term broadcasting describes how numpy treats arrays with different shapes during arithmetic operations. Subject to certain constraints, the smaller array is “broadcast” across the larger array so that they have compatible shapes.