[Jtsummers]

https://en.wikipedia.org/wiki/ALGOL_58

ALGOL, the := in programming languages used for assignment comes from IAL which became ALGOL 58. It's definitely not a modern development. Go reintroduced it to popular mainstream languages, sort of. Except they still use = for assignment and := is used when it's also declaring a new variable.

[int_19h]

:= for assignment ultimately comes from math, as do most operators in early Algol: https://www.masswerk.at/algol60/report.htm#2_3