“The most likely suggestion is that it comes from a monogram made of the first three letters of the Greek name for Jesus.
In Greek, “Jesus” is ΙΗΣΟΥΣ in uppercase letters and Ἰησοῦς in lower. The first three letters (iota, eta, and sigma) form a monogram, or graphic symbol, written as either IHS or IHC in Latin letters.”
—Patricia T. O’Conner and Stewart Kellerman, “The ‘H’ in ‘Jesus H. Christ’.” Grammarphobia. February 2019.
- “A good Christian can not attend church and still be saved.”
- “A good Christian cannot attend church and still be saved.”
“Example 1 speaks uncontroversially of the possibility that good Christians may be forgiven for lax church attendance. Example 2, by contrast, states a radically anticlerical claim: that church attendance will wreck your chances of salvation.”
—Geoffry Pullum,”A Moment of Sympathy for the Old Fogeys and Snoots.” The Chronicle of Higher Education. October 28, 2018
Even if general usage would make these interchangable, I cannot abide using can not and cannot as if they were the same.