To align with Delphi language. COMMA is used when passing arguments, SEMICOLON is used to declare parameters. Neither of them are perfect but I think Comma is better suited.
It is also compatible with DUnitX. (Less trouble when transition)
The plural name implies that more than one delimiter could be supported. I suggest change it as single delimiter. If we choose Comma,
;can/should be used to in other cases. e.g.
procedure Test(strings: TStrings; values: array of string; connectionStringDelimiteredBySemicolon: string);