"hadst one ship come in" is a phrase that refers to the arrival of a single ship. There are several synonyms that can be used to replace this phrase, including "if only one vessel arrived," "if a solitary ship docked," "had only a lone vessel arrived," "if but one ship came in," and "if only a solitary boat arrived." Each of these alternatives conveys the same message that a single ship has arrived or would have made a difference. These synonyms can be used to add variety to writing or to avoid repetitive language.