"To rail someone" means to have vigorous sex with someone. I believe the poster to whom you replied was making a joke about the name being unfortunate.
Naming is hugely important. I'm always catching downvotes on here for complaining about otherwise-decent open source projects that will never gain traction because they have moronic names like Xonaly or whatever. But I suspect "hey can you rail me 20 bucks" won't be how it gets referred to, and "I don't have cash, does e-transfer work?" will continue to be how it's referred to.
Acxsys [1] was launched by the Canadian banks in 1996 as a for-profit startup meant to develop online payment solutions, and they original launched the service as "certapay".
Acxsys was folded into Interac in 2018, but I think it was somewhat prior to that the certapay name was discontinued in favour of "email money transfer". Everyone called them e-transfers though, and so eventually Interac gave up on EMT and just went with that name, which is what it is now: https://www.interac.ca/en/resources/personal-resources/perso...