Where does “lazy-ass” come from?

lazy-ass (English) comes from English ass, from Middle English asse, from Old English assa, from Old English assen, from Latin asinus, from Latin acinus, from Latin acies, from Proto-Indo-European h₂eḱ- — sharp.

Ancestry of “lazy-ass”, step by step

lazy-ass traces back through two separate lines of ancestry.

via English ass

StepLanguageWordMeaning
1EnglishassAny of several species of horse-like animals,...
2Middle EnglishasseAlternative form of axen
3Old Englishassaass, donkey
4Old Englishassenshe-ass
5Latinasinusa donkey, an ass; an ass, an idiot, a dolt, a...
6Latinacinusa berry, especially the grape; the seed of a...
7Latinaciessharp edge or point; battle line; battle,...
8Proto-Indo-Europeanh₂eḱ-sharp

via English lazy

StepLanguageWordMeaning
1EnglishlazyUnwilling to do work or make an effort;...
2Middle Low Germanlasichslack, languid, idle; slack, feeble, lazy
3Middle Low Germanlaspatch, scrap; tired, dull; salmon
4Old Saxonlahs
5Proto-Germaniclahsazsalmon
6Chinese拉薩
7Tibetanལྷ་སLhasa
8Old Tibetanར་ས
Every word from Proto-Indo-European h₂eḱ-