The Great Gatsby, peculiar combination of circumstances

Could you please tell me the meaning of "peculiar" in the following excerpt from the chapter Three of The Great Gatsby:

A chauffeur in a uniform of robin’s egg blue crossed my lawn early that Saturday morning with a surprisingly formal note from his employer—the honor would be entirely Gatsby’s, it said, if I would attend his “little party” that night. He had seen me several times, and had intended to call on me long before but a peculiar combination of circumstances had prevented it—signed Jay Gatsby in a majestic hand.

Thank you.