If you want Hugin to auto-recognize and correct for the lens, then probably the right tag to use is Samyang 8mm f/3.5 Fish-Eye CS, because this is the entry in the lensfun database, which is now integrated into Hugin use. In the slr-samyang.xml file the entry is:
<model>Samyang 8mm f/3.5 Fish-Eye CS</model>
<model lang="de">Samyang 8mm f/3.5 Fischauge CS</model>
<mount>Nikon F AI</mount>
<mount>Micro 4/3 System</mount>
<!-- Taken with some APS-C Pentax probably. -->
<tca model="poly3" focal="8" br="-0.0007764" cr="0.0013798" vr="1.0000228"
bb="-0.0002711" cb="0.0008531" vb="0.9998496" />
<!-- Taken with Nikon D7100 -->
<distortion model="ptlens" focal="8" a="0.04098" b="-0.15413" c="0.11977" />
The lens is manufactured by Samyang in Korea, but is generic-branded with many many names: Rokinon, Vivitar, Falcon, Walimex, Bower, Opteka, Bell and Howell, Polar, Phoenix, and Pro-Optic are among the many names of Samyang. Weirdly, Vivitar calls it a 7mm, and Pro-Optic a 6.5mm, but they're all the same lens with the same stereographic mapping.
Also, there's an easier way than going to the command line to tag up lenses. I own a Rokinon 7.5mm f/3.5 fisheye for the micro four-thirds mount, as well as adapting several manual lenses for my Canons. I tag up the EXIF for all my manual lens and scanned film images in Lightroom with the LensTagger plugin. LensTagger is a GUI frontend for exiftool, which makes the job much easier than typing the command by hand on the command line every time. It can save "presets" of specific lenses you use often, and writes the following fields:
The Lens and LensModel fields can take any string, and will, indeed show up in Lightroom intelligibly. You don't need to worry about numeric coding in this case. When in Lightroom, you can set up the lens profile default for whatever tag you come up with. I tag my Rokinon 7.5 shots with "Rokinon 7.5mm f/3.5 UMC fisheye", and then set it to default to Stereographic remapping with kenw's Samyang 7.5 f/3.5 lens profile for lens correction. I'm sure there's a profile out there for the dSLR 8mm version.