I believe Heglar " COINED" the Term " SLIDER " as a Name for a style of a call he made and Named it the " SLIDER ". You will find this with several older calls, the Older makers coined them up and NAMED THEM, now instead of being a re-make of a STYLE of Call from Old, they are termed as a style of call exclusively made and named by a call maker, instead of just a Style that they made better, or copied in what-ever way.
Since he named THAT call a SLIDER, all that follow, can not use the name slider, also, anyone who makes this STYLE of call, is now thought to be infringing on his named call, the "SLIDER", which is now thought of as a Heglar Design, instead of a STYLE of call only, that has been made for many years.
You really only see this in the Trumpet, Yelper Turner world. Except, for the Strumpet and Biscuit of course, they catch a bit of heck as well.