Ameslan, which stands for "American Sign Language," is an old term used in the 1960s and has been obselete since then. However, it is resurfaced in some places nowadays. Louie J. Fant, Jr. wrote one of the early published books, "Ameslan: an introduction to American Sign Language" in 1972.
At that time, there was a confusion between Siglish (later called "Signed English") and Ameslan. Louie attempted to clarify confusions and explained the difference. Simply put, Ameslan or ASL is a language of its own. "Siglish", later known as Signed English, is a signed language in English grammatical order. In my past essay, I described an equivalent of Signed English to coercing Chinese children to learn and write Chinese characters in English grammatical order. Amseslan/ASL and Chinese have more common in grammar than English.
Also see: American Sign Language: a language of North America.