Ever considered this?
A thing that passes by is a bypass.
However, a person who passes by isn’t a *bypasser but a passer-by.
A thing that stands by should therefore be a *bystand, but it isn’t, it’s a standby.
However, a person who stands by isn’t a *stander-by but a bystander.
My head hurts.
I under stand.
Ah, that makes you a stander-under 😛