Where does “vainful” come from?

vainful (English) comes from English vain, from Old French vain, from Latin vānus, from Italian vano, from Italian vanare, from Romanian -re, from Latin -āre, from Proto-Italic -āō — he, she.

Ancestry of “vainful”, step by step

vainful traces back through two separate lines of ancestry.

via English vain

StepLanguageWordMeaning
1EnglishvainOverly proud of oneself, especially concerning...
2Old Frenchvain—
3Latinvānusvain, empty, vacant, void
4Italianvanovain, useless, idle; quaint; space, opening,...
5ItalianvanareAlternative form of vaneggiare
6Romanian-re-ing, -ation
7Latin-ārefirst conjugation
8Proto-Italic-āōForms primarily denominative verbs
9Proto-Indo-European-eh₂yétiCreates iterative/ frequentative/ intensive...
10Proto-Indo-European-yétiCreates intransitive, often deponent,...
11Proto-Indo-Europeanyé-—
12Chichewaiyehe, she

via English ful

StepLanguageWordMeaning
1Englishful—
Every word from Chichewa iye →Every word from Romanian -re →Every word from Proto-Indo-European -yéti →