萬一

just in case / if by any chance / contingency

surname Wan

ten thousand / a great number

one / single / a (article) / as soon as / entire; whole; all; throughout / "one" radical in Chinese characters (Kangxi radical 1) / also pr. [yao1] for greater clarity when spelling out numbers digit by digit

to guard against the unexpected (idiom); just in case / prepared for any eventualities

better to be safe than sorry (proverb) / to be prepared just in case