Where does “幽霊文字” come from?

幽霊文字 (Japanese) comes from Japanese 文字, from Middle Chinese 文字.

Ancestry of “幽霊文字”, step by step

幽霊文字 traces back through two separate lines of ancestry.

via Japanese 文字

StepLanguageWordMeaning
1Japanese文字a letter, a character; script, writing system; a...
2Middle Chinese文字—

via Japanese 幽霊

StepLanguageWordMeaning
1Japanese幽霊a ghost, a phantom
2Middle Chinese幽靈—
Every word from Middle Chinese 文字 →Every word from Japanese 文字 →