From V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016) :
HPUX
Hewlett Packard / UniX (Unix), "HP/UX"
From The Free On-line Dictionary of Computing (30 December 2018) :
HP-UX
The version of Unix running on
Hewlett-Packard workstations.
HP-UX conforms to X/Open's Portability Guide Issue 4
({XPG4), Federal Information Processing Specification (FIPS)
151.1, POSIX 1003.1, POSIX 1003.2, AT&T's System V
Interface Definition 2 ({SVID 2). HP-UX incorporates
selected features from the University of California at
Berkeley Software Distribution 4.3 ({4.3BSD).
It is known by some as "{HP-SUX".
[Features?]
(1997-05-12)