Late 17th century; earliest use found in John Humfrey (bap. 1621, d. 1719), clergyman and ejected minister. From un- + classical Latin percept-, past participial stem of percipereperceive + -able.
Definition of unperceptable in US English:
unperceptable
adjective(ˌ)ʌnpəˈsɛptəbl
rare, non-standard
= unperceptible.
Origin
Late 17th century; earliest use found in John Humfrey (bap. 1621, d. 1719), clergyman and ejected minister. From un- + classical Latin percept-, past participial stem of percipere perceive + -able.