“The expression ‘negotiable instrument’ is one of variable meaning, and what is meant thereby often can be determined only by the context… Primarily ‘negotiable’ indicates transferability with a certain facility…..
“It may be not without interest to consider how instruments gain the negotiable quality and to trace, sketchily perhaps, the process of recognition.”
Aigler, Ralph W. "Recognition of New Types of Negotiable Instruments." Colum. L. Rev. 24, no. 6 (1924): 563–93.