Today's pattern is yet another that seems to be difficult to find info on - That said, I'll share what I was able to actually find!
The Clasp pattern can actually refer to many different knives; sometimes called a Case Buffalo or Bulldog. In any event, the signature of this pattern is the tail bolster that arcs upward, as seen in the photo below.
This knife was traditionally produced on the Case pattern #72; and was largely discontinued prior to 1940. However it made a short comeback just 20 some years later in a run from 1965 to 1969.
From there, its assumed that the pattern wasn't used until 2010 when Case put out a number of vintage patterns. That's where the knife pictured above comes from. The knives themselves had mainly bone handles with a single, wide Clip blade.
As for *WHY* it's was called, the best answer I can find is because it IS a Clasp knife- that being a hinged blade.
My personal opinion is that this is a pattern than inspired things like the Large F0lding Hunters that we see today. Whether that's actually what happened, I can't say with any certainty.
As for the reasoning behind the other nicknames - Buffalo and Bulldog - I can't really find an answer! SO if you know, we'd love to learn about it! That's the whole point of this after all - to learn! So if you see something we got wrong or know something we left out, feel free to comment it!