From The Free On-line Dictionary of Computing (19 January 2023):
RUSH
1. <language> An interactive dialect of PL/I, related to
CPS, dated about 1966. The name is the abbreviation of
"Remote Use of Shared Hardware".
["Introduction to RUSH", Allen-Babcock Computing 1969. Sammet
1969, p.309.]
2. <language> A high-level language that closely resembles
Tcl but aimed to provide substantially faster execution.
See An Introduction to the Rush Language
(ftp://ginsberg.cs.berkeley.edu/pub/papers/asah/rush-tcl94.ps.gz).
by Adam Sah, Jon Blow, and Brian Dennis (1994).
(1996-12-17)