i Register
In some senses, johnny-come-lately is marked as idiomatic. Watch for register when choosing this word.
noun
A newcomer; a novice; an upstart.
She might take offense if some Johnny-come-lately thinks he can do a better job.
Morris now shared financial decisions with a woman, a female Johnny-come-lately. Imagine the eventuality of Morris's share of their fortune ever falling into such Johnny-come-lately hands. God forbid!
noun
Alternative form of Johnny-come-lately.