Triskaidekaphobia

Technically, Triskaidekaphobia is from the Greek: tris meaning "3," kai meaning "and," and deka meaning "10", denoting a phobia, meaning a fear, of the number 13.
It is a superstition related to a specific fear of Friday the 13th, called paraskevidekatriaphobia or friggatriskaidekaphobia.

Rico says that, regardless of the derivation, it was still startling to realize that tomorrow is, indeed, going to be Friday the 13th. Not that he's superstitious, mind you, but you never know...