Not familiar with the term "Huckleberry" in relation to holster design. I think "Huckleberry" derived primarily from Mark Twain's (Samuel L. Clemens) character Huckleberry Finn, and described a disruptive or distracting, probably undesirable, influence in one's life.

Famed Pinkerton detective (and author) Charles Siringo carried his Colt Single Action Army .45 in a shoulder holster that he described as a "J.W. Hardin" holster, referring to notorious outlaw John Wesley Hardin who reportedly carried a Colt .36 Navy revolver in that type of holster. Charlie Siringo's active period was late-1880's to about 1910, knew Billy the Kid personally, worked with Tom Horn while with Pinkerton's Denver office, was part of the long hunt for Butch Cassidy and the Sundance Kid (Hole in the Wall Gang), later worked as a technical adviser for early western motion pictures, probably knew what he was talking about (although he was rather self-promoting in much of his writing).

Another common carry method during the late 19th Century and early 20th Century was to have a special trouser pocket accepting a leather holster-like liner, usually on the outer side of the trouser leg. Trouser waists were much higher during that period, and suspenders (braces, galluses, whatever you want to call them) were much more common than trouser belts. Shoulder holsters of that period were usually designed to position the handgun less under the armpit, more forward in the left breast-ribcage area, frequently angled to present the butt forward (not so much concealment rigs as they were designed for ready access to the gun).