American Sign Language (ASL) is the natural and preferred language of the Deaf community in both the United States and Canada. Woodward (1978) estimated that approximately 60% of the ASL lexicon is derived from early 19th century French Sign Language, which is known as "langue des signes francaise" (LSF). The lexicon of LSF and ASL may be derived from several sources such as gestures, home signs created by deaf individuals living with their hearing families, North American Indian sign languages, Martha Vineyard sign language, and new signs added to LSF and ASL through the generations. Before the emergence of LSF in the 18th century and ASL in the 19th century, Cistercian Sign Language (CSL) had been used extensively by monks for centuries in Europe. This dissertation explores the plausible roots of ASL prior to LSF. These ancestral roots were researched: (A) to determine, from a limited corpus of CSL, if similar phonologically and semantically related lexical items are found in LSF and ASL; (B) to determine if any of the CSL, LSF and ASL phonologically and semantically related lexical items are related simply because they are iconic forms; and (C) to determine if any of the CSL, LSF and ASL phonologically and semantically related lexical items are initialized. Analysis of the data revealed that there are numerous identical and similar signs between CSL and Early LSF, and among CSL, LSF, and ASL, indicating that lexical borrowing from CSL was a factor in the development of LSF and ASL. There is a strong likelihood that iconicity accounts for many of the identical and similar lexical signs that are shared among these three signed languages. There is limited evidence of the employment of initialization in the lexical borrowing that took place from CSL to LSF, and then to ASL. This analysis of lexical borrowing provides new information about the historical roots of LSF and ASL and their origins in CSL. Information about the development of ASL, and how CSL and LSF have had an impact on the present-day ASL lexicon, is a significant aspect of ASL literature and is important to include in Deaf Studies and ASL teaching curricula. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]