From mboxrd@z Thu Jan  1 00:00:00 1970
From: doug@cs.dartmouth.edu (Doug McIlroy)
Date: Tue, 31 May 2016 03:27:43 -0400
Subject: [TUHS] etymology of read -u
Message-ID: <201605310727.u4V7Rhmp030422@coolidge.cs.Dartmouth.EDU>

What's the mnmonic significance, if any, of the u in
the bash builtin read -u for reading from a specified
file descriptor? Evidently both f and d had already been
taken in analogy to usage in some other commands.

The best I can think of is u as in "tape unit", which
was common usage back in the days of READ INPUT TAPE 5.
That would make it the work of an old timer, maybe Dave Korn?