Where does “unmercifulness” come from?

unmercifulness (English) comes from English unmerciful, from English merciful, from Middle English merciful, from Middle English mercy, from Middle English -ful, from Old English -ful, from Proto-Germanic -fullaz, from Proto-Germanic fullaz — to fill.

unmercifulness (English): The state or condition of being unmerciful

Definitions

  1. The state or condition of being unmerciful

Ancestry of “unmercifulness”, step by step

unmercifulness traces back through two separate lines of ancestry.

via English unmerciful

StepLanguageWordMeaning
1Englishunmercifulnot showing mercy
2Englishmercifulshowing mercy
3Middle Englishmerciful
4Middle EnglishmercyAlternative form of mercien
5Middle English-fulAppended to nouns to form adjectives denoting...
6Old English-fulfull of; -ful
7Proto-Germanic-fullaz-ful
8Proto-Germanicfullazfull; the whole, the entire
9Proto-Indo-Europeanpl̥h₁nósfull
10Proto-Indo-Europeanpleh₁-to fill

via English Ness

StepLanguageWordMeaning
1EnglishNessAn Ulster princess and the mother of Conchobar mac Nessa and Findchoem in the Ulster Cycle of Irish mythology. Daughter of Eochaid Sálbuide. Also the mother of Cormac Cond Longas by incest with Conchobar mac Nessa
2Middle Englishnesse
3Old Englishnæsnot, not at all; not; first/third-person singular...
4Proto-Germanicnasjąfoothill; headland; cape
5Proto-Indo-Europeannéh₂snose
Every word from Proto-Indo-European pleh₁-Every word from Proto-Indo-European pl̥h₁nósEvery word from Proto-Germanic fullaz