I have a friend who in the two-three years I've known her will say "whileas" wherever I or other English speakers I know would say "whereas". She is a native English speaker and has read extensively (mostly fantasy, but has read some Shakespeare, if for some reason the Bard uses this construction). We're guessing at this point that she sourced it from her mother, who also says it.
Googling reveals that there are some usages of "whileas" (or "while as") in older texts, such as The Book of a Thousand Nights and a Night (Yes, really). Merriam-Webster says it's archaic, and a "helpful" commenter adds that "a highly educated person uses whileas in place of whereas".
However, I don't have access to the OED to see more of its history. Could anyone enlighten me? When was this used? Was it always a lesser-used form of "whereas"? Any historical background you could give me would be much appreciated. Also, is there any place one would just pick this word up without being a reader of original medieval literature?
Examples of friend's usage:
"A square has four sides, whileas a triangle has three."
Other usage: https://www.wordnik.com/words/whileas
A book with a super long title also uses this construction: link