no
"not in any degree, not at all," Middle English, from Old English na, from ne "not, no" + a "ever." The first element is from Proto-Germanic *ne (source also of Old Norse, Old Frisian, Old High German ne, Gothic ni "not"), from PIE root *ne- "not." Second element is from Proto-Germanic *aiwi-, extended form of PIE root *aiw- "vital force, life, long life, eternity." Ultimately identical to nay, and the differences of use are accidental.