An early Australianism (circa early 20th century), said during moments of anxious expectation, generally after the commencement of moments of chance, for example awaiting imminent news; the results of a sports match, or an attempted task with an unknown, random result.
Historically the phrase entered the vernacular in the first half of the 20th century, coined during betting matches of 'two-up', but the etymology may stem from roulette.
During a dice roll, while still shaking the dice: "Come in, spinner!"
Often refers to telling someone to come spend time with you or to come shop (do business) with you. Can also be used aggressively to antagonize an op. This phrase has various connotations depending on the context.
I'm just getting off work, but you can still come fuh with me.