That's a holdover from early English settlers. Even today, Brits who speak the Queen's English put an "r" or "hr" at the end of a word ending with "a", such as "PAStahr" (Italian noodles).
And Rod Stewart does this in his songs.
"Leave Virginia-er alone"
As does Elton John "It'll take you a couple of vodker-and tonics...to get you on your feet again"
Obviously they were teased, because on the live version, Elton sings "VODKA and tonics" emphasizing the word.